DEAR ABBY: I am a 20-year-old male and a full-time college student. On nights and weekends I hold down two part-time jobs. One of them is delivering pizza.

One night two weeks ago, I made a delivery to a nearby motel. As I was leaving, I saw a familiar car pull into the parking lot. It was my mother's Mustang. She was driving.

I was surprised to see her there, so I turned my car around and followed her to the rear of the motel. I watched her park, get out, knock on a door and enter. After several minutes of confusion, I returned to my job.

Two hours later, after more deliveries, I returned to the motel. Sure enough, her car was still parked in the same spot. After 20 minutes or so, I watched her come out of a room with a man I recognized from her office. He's in his late 20s, and I know he has a wife and two small children. (Mother is 41, but looks younger.) I froze. I didn't confront her.

Now I don't know what to do. Every time I look at my dad I feel guilty because I haven't said anything. The news would crush him. Should I continue keeping this to myself or tell someone? -- IN SHOCK IN CHICAGO

DEAR IN SHOCK: It is unfortunate that you have been caught in the middle. The person you should talk to is your mother. Your father needs to be told, but she is the one who should do it. If her co-worker is cheating on his wife with your mother, he could also be cheating with others. In that case, your parents should both be tested for sexually transmitted diseases (STDs).

DEAR ABBY: My husband, "Howard," and I are in our early 40s with two young children. I have had a problem with my father-in-law my entire marriage. He expects Howard to entertain him on weekends. As it is, they see each other Monday through Friday because they work together. My father-in-law is married, but he doesn't want to be home with his wife on weekends -- he'd rather spend time fishing or bowling with his son.

I think Howard should be with our children and me on the weekends. When I complain to him about it, Howard accuses me of nagging. This Saturday morning when I objected, Howard stalked out and said over his shoulder, "See you tonight!" It's impossible to make plans for the weekends because Howard won't agree to anything until he checks with his dad first to see if HE wants to do something.

Am I selfish to want my husband's attention for our children and me on weekends? After all, his dad already sees him far more than we do. Should I try to accept this, or tell my husband to either grow up or move in with his dad? Please help me, Abby. The tension between us is unbearable. -- DESPERATE WIFE IN TENNESSEE

DEAR DESPERATE WIFE: Your father-in-law is, and has been, a terrible role model for his son. Your husband is no longer a child; he is a grown man with responsibilities of his own that he is shirking.

Since Howard doesn't want to hear it from you, your next move should be to get some marriage counseling. If he won't go with you, take your mother-in-law and go without him. It may come to light that because of their business relationship, Howard feels he can't say no to Dad for fear of jeopardizing his financial obligations to you and the children. Whatever the reason, it needs to be brought out into the open.

For an excellent guide to becoming a better conversationalist and a more attractive person, order "How to Be Popular." Send a business-size, self-addressed envelope, plus check or money order for $5 (U.S. funds only) to: Dear Abby Popularity Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included.)

DEAR ABBY: Yesterday I saw a little boy left alone in a parked car. The windows were rolled down about 2 inches. The child, probably 1 year old, was strapped in a child seat in the back of the vehicle. It was a hot day and the car was sitting in the sun.

I was going into the library, so I hoped that the parent would only be gone long enough to return a book. However, when I came out, the child was still there. I got into my car and was about to call the police, but before I did, the parent came out and drove away. I did jot down the license number.

I couldn't get the little boy out of my mind, so I phoned to report the incident to the police this afternoon. Perhaps it will keep that parent from doing it again. I know I should have taken action the moment I saw the child, and I feel guilty that I did not.

Abby, please remind your readers that children should NEVER be left alone in a car. Anyone who sees a child in an unattended car should phone the police immediately. I'm glad the baby didn't die because of my inaction. -- ILLINOIS PARENT

DEAR ILLINOIS PARENT: Thank you for a timely reminder. Health experts warn that on a breezy day with the temperature only in the low 70s, the interior of a closed automobile can heat up to 125 degrees in 15 minutes. Even with the window cracked, a child could dehydrate within minutes -- with deadly results. And the same goes for pets.

DEAR ABBY: I am a 17-year-old boy with a big problem. There's this girl, "Ashley," I really care about. But I don't know how to tell her. I took her to the junior prom and afterward we spent most of the night together -- talking.

That night I realized how much Ashley and I have in common and how much I care for her. The trouble is, it's summer vacation, and it seems like she's always too busy to go out with me, or she already has plans.

We talk almost every day, but I need to see her and be with her. Abby, I know no one is perfect, but Ashley is the closest thing to it.

Yesterday I broke down and cried because I realized how much I want her to be mine. Can you please tell me what to do -- and how to tell her my feelings? I ache inside. -- SMITTEN IN OHIO

DEAR SMITTEN: Look at the bright side:

(1) Ashley obviously likes you. The two of you talk on the phone nearly every day. Tell her you really like her. It's a compliment and it's the truth.

(2) You shared a wonderful night at the prom. It is something the two of you will never forget.

Perhaps this will have to do for now. Summers fly by quickly, and soon you will have more school events to share. In the meantime, make plans with other friends and stay active. It will keep you from dwelling on the fact that you're not with Ashley as much as you'd like to be.

DEAR ABBY: Your recent letter regarding tattoos reminded me of an incident I'd like to share. Last year I was in a nail salon in Hawaii, waiting for a manicure and a pedicure. Waiting with me were two ladies well into their 60s.

A girl of about 20 strolled in and sat down across the room from us. She was wearing a low-cut top, so we couldn't help but notice a prominent rose tattoo high on her breast.

One of the women leaned over to the rest of us and whispered, "Little does she know that when she's in her 50s, she'll have a long-stemmed rose!" -- KATHLEEN IN WASHINGTON STATE

DEAR KATHLEEN: If you didn't laugh out loud, you deserve a bouquet of roses.

What teens need to know about sex, drugs, AIDS, and getting along with peers and parents is in "What Every Teen Should Know." To order, send a business-size, self-addressed envelope, plus check or money order for $5 (U.S. funds only) to: Dear Abby, Teen Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included.)

DEAR ABBY: I am a 29-year-old married woman, and I dearly love my husband and child. However, I think I've fallen head over heels for my "first love" (I'll call him Cliff) all over again.

I recently ran into Cliff at the hardware store, and after talking a while, we went riding around in his car -- just like we did when we were in high school. Then we parked and started making out.

Cliff confessed that for the past 10 years he's felt HE was meant to be my husband, and letting me go was the biggest mistake of his life. The terrible thing is, now I'm wishing I had married him, too.

For the past month we've been secretly meeting downtown three times a week. All we do is drive around, park and neck -- nothing more. When I'm with him, I feel like a teenager again. I still love him, Abby, and I'm so confused I cry in my pillow. Sign me ... BACK IN LOVERS' LANE

DEAR BACK IN LOVERS' LANE: You may be just "two teenagers in love" in your fantasies, but in reality you're two adults who are begging for trouble. You're playing a dangerous game that could devastate your husband and affect your child. Before any more clandestine meetings, it's time to sit down and sort out what's really important to you. Counseling can help you discover what is missing in your marriage that has made a second adolescence so appealing. Don't put it off.

DEAR ABBY: I need some advice. My boyfriend and I have been together for two years. He was adopted by loving parents who gave him everything. But he has just found his birth mother, and they seem to want to catch up on lost time.

My problem is I can't seem to stop resenting that his mother came back into his life. I feel very left out, and as if my time has been usurped by another woman. Don't get me wrong. I am happy for him, but I no longer feel that I am his No. 1 priority.

I tried talking to my boyfriend about this, and he acts like he understands my feelings -- but he also says it seems I want him to choose.

How can I stop feeling this way? -- LEFT OUT IN LAREDO

DEAR LEFT OUT: First of all, understand that what is going on is not about you; it's all about him and his need to understand who he is and where he came from. Like any new relationship, it is distracting in the beginning, but will subside in time. So be patient. Realize that what a man feels for his mother is not what he feels for his girlfriend. Don't take this personally, and above all, do not allow yourself to be put into a "her or me" situation. If you do, you might win the battle, but you'll surely lose the war.

DEAR ABBY: I am a 16-year-old male student and I have a huge crush on my summer school teacher, "Miss Bodacious." She doesn't notice me and it's driving me crazy. I'm losing my mind. I hate it! Please help. What should I do to calm my raging hormones? -- GOT IT BAD FOR "BOD" IN DELAWARE

DEAR GOT IT BAD: In a word, SUBLIMATE. It's time to take the energy you are devoting to fantasizing about your teacher and channel it into something else -- like sports activities. Not only will it give you less time to think about "Miss Bodacious," but you'll be so tired when you're done that you won't have the energy. (Cold showers also help.) Good luck!

For an excellent guide to becoming a better conversationalist and a more attractive person, order "How to Be Popular." Send a business-size, self-addressed envelope, plus check or money order for $5 (U.S. funds only) to: Dear Abby Popularity Booklet, P.O. Box 447, Mount Morris, IL 61054-0447. (Postage is included.)