DEAR ABBY: I desperately need some advice. I am a physician, married to a beautiful woman for 20 years, and we have three teen-age children. My wife and I are in our 40s.

In 1995, my wife confessed she had a seven-year affair with my best friend. He would come to our house after I went to work and they would have sex in our bed. Although my wife never showed me any affection during that period, I blamed it on the strain of raising three children, never suspecting her infidelity.

She let word of the illicit affair slip when I teased her about her old boyfriends. I was devastated, but I didn't let on. She apologized, and our marriage continued for the sake of the children. In the last two years, my wife has been especially loving and affectionate toward me.

Earlier this year, my married sister-in-law (I'll call her Marie) stayed with us for four months. She confided to me that she had an unsatisfactory sex life with her husband. One thing led to another, and we slept together several times. Marie has since returned home.

Now I feel guilty and would like to confess this indiscretion to my wife to clear my conscience, but I am not sure how she'll react.

Though it will even things out, I do not want to hurt my wife or expose Marie's behavior. Should I tell my wife about the affair with her sister? -- ONLY HUMAN IN KENTUCKY

DEAR ONLY HUMAN: I question your motives for confession. Remember the pain that your wife's confession caused you? While confessing may be good for the soul, it will undoubtedly hurt others. I suggest you confess to your clergy instead.

DEAR ABBY: A few years ago, you printed a piece about a place called "The Rainbow Bridge" -- where our pets go when they die.

Often, over the last few years, I wish I had saved the article to give to friends whose pets have passed away. I try to tell them about it, but I know I can't do justice to the beautifully written tribute.

I'm sure if you reprinted it, many would find comfort from it. -- WAITING HOPEFULLY, MIDDLESEX, MASS.

DEAR WAITING HOPEFULLY: It has been several years since I printed "The Rainbow Bridge," and I'm pleased to share it once again:

THE RAINBOW BRIDGE

There is a bridge connecting Heaven and Earth. It is called the Rainbow Bridge because of its many colors. Just this side of the Rainbow Bridge, there is a land of meadows, hills and valleys with lush green grass.

When a beloved pet dies, the pet goes to this place. There is always food and water and warm spring weather. The old and frail animals are young again. Those who are maimed are made whole again. They play all day with each other.

There is only one thing missing: They are not with their special person who loved them on Earth. So, each day they run and play until the day comes when one suddenly looks up! The nose twitches. The ears are up. The eyes are staring. And this one suddenly runs from the group.

You have been seen, and when you and your special friend meet, you take him or her in your arms and embrace. Your face is kissed again and again and again, and you look once more into the eyes of your trusting pet.

Then you cross the Rainbow Bridge together, never again to be separated.

To receive a collection of Abby's most memorable -- and most frequently requested -- poems and essays, send a business-sized, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby's "Keepers," P.O. Box 447, Mount Morris, Ill. 61054-0447. (Postage is included.)

DEAR ABBY: The number of people who take the time to write a letter, address it, stamp it and mail it only to complain about ridiculous, everyday things blows my mind. The lady who wrote complaining that restaurants don't slice lemons the way she likes them for her iced tea flabbergasted me. Maybe she should take a reality check.

When someone or something starts getting on my nerves, I find that taking a moment to think about its importance in the grand scheme of things really helps. This may seem morbid, but I do so by imagining that I am on my deathbed. Think about it: Do I want to lie there and say, "I've had a wonderful life full of challenges, beauty and love," or do I want to say, "I should have worried more about that snotty salesperson, or the paperclip requisition form"?

We can't all be easygoing all the time -- and we shouldn't be -- but the key is keeping things in their proper perspective.

Abby, the advice you gave the lemon-wedge lady was right on. If she doesn't like what's offered, she should bring her own darn lemons. That's a pretty good concept to keep in mind when it comes to just about anything. -- MONIQUE BYRNE, FREMONT, CALIF.

DEAR MONIQUE: Thank you for your support. I received a fistful of criticism for having printed that letter. Read on for a sample:

DEAR ABBY: I'm writing in response to "Incognito," who wrote to complain about her lemons being sliced instead of being cut into wedges in restaurants. Abby, I am only 16 years old, but I have enough sense to keep my mouth shut about small things. If I ever complain about my lemons being sliced wrong, I would hope to God that someone would slap my face.

There are people starving all over the world who would love to have a sliced lemon. I think your response to "Incognito" was way out of line. You told her it would be a "no-brainer" for chefs to provide lemon wedges. HELLO? Lemon wedges?

Abby, with all the problems we have in the world today, lemon wedges should be the least of our worries. Don't you think that a more appropriate response to "Incognito" would have been, "Get over it!"? I do. -- SKYLAR HOLBROOK, MIDLOTHIAN, VA.

DEAR SKYLAR: Not all problems are of equal importance to all people. I thought "Incognito's" letter provided an interesting change of pace and I'm sorry you did not agree that it was worthy of my column. Telling people to "get over it" is not very helpful; furthermore, it's not my style. I'm here to help my readers.

DEAR ABBY: Ever since you printed the letter from the lady who said that reading sexy books had improved her sex life, romance and sexy books have been flying off the shelves, according to the Friends of the Library bookstore here in Hot Springs, Ark.

There used to be a glut of these books in the store, but now the managers are begging for more books to be donated to fill the shelves again. What a novel way to promote literacy. -- FRIENDS OF THE LIBRARY VOLUNTEER

DEAR FRIENDS VOLUNTEER: If it's getting the job done, then I'm all for it. I have always encouraged people to read, read, read. Read for information and read for pleasure. Our libraries are filled with knowledge and joy, and it's all there, free for the taking.

Abby shares more of her favorite, easy-to-prepare recipes. To order, send a business-size, self-addressed envelope, plus check or money order for $3.95 ($4.50 in Canada) to: Dear Abby, More Favorite Recipes, P.O. Box 447, Mount Morris, Ill. 61054-0447. (Postage is included.)

DEAR ABBY: My son and his wife are both 40 years old. They have been happily married for more than two years. Although we have a loving relationship with them, an important element in our lives is missing.

They have not yet produced a child. They tell us she cannot conceive without medical help. My husband and I are in our 70s. We were told not to mention the childbirth subject, as it is a sensitive one. They claim to be "trying," but reveal nothing else.

My question: Do we have the right to ask them specifically what measures, if any, they have taken to help nature along? Dare I tell them that we feel cheated at not having a grandchild? May we speak of adoption to them? I feel this is a family concern, not just their problem. -- WANTS TO BE A GRANDMA IN L.A.

DEAR WANTS: You would be a mile out of line to harp on your desire to be grandparents, and to pry into your son and daughter-in-law's personal lives. They have already told you the subject is a sensitive one. Listen to them, and for heaven's sake, keep your questions to yourselves!

DEAR ABBY: I'm writing in response to the letter from Charles F. Yarham, who wrote about his pet peeve. The last line of his poem was, "Is when a kid is called a 'sibling.'"

The useful term "sibling" never gets me riled,

It's a sister or a brother, whether adult or child.

But what gets MY "goat" (and always did),

Is when a human child is called a "kid"!

-- MAGGIE RITCHEY, LOS ANGELES

P.S. Actually, Abby, the above is a fib. I quite often use the term "kid" inappropriately, but I couldn't resist!

DEAR MAGGIE:

'Tis a pity

Chuck Yarham's ditty

Within contained

The very thing his verse disdained.

DEAR ABBY:

There are words in English that irk us all,

From me you'll get no quibbling.

And the one that drives me up a wall

Is when a kid is called a "sibling."

-- RENEE IN ALABAMA

DEAR ABBY:

The only time that "sibling" irks

Is when the kid's a baby goat.

I say English is, with all its quirks,

The bestest language ever wrote!

-- MICHELLE LEE, LONG BEACH, CALIF.

DEAR ABBY: In response to Charles Yarham's poem:

When I read your little poem,

A gasp came from my throat.

"Siblings" are our kinfolk,

But a "kid" is just a goat!

-- JAMES WICKINSON, RICHMOND, VA.

Everybody has a problem. What's yours? Get it off your chest by writing to Dear Abby, P.O. Box 69440, Los Angeles, Calif. 90069. For a personal reply, please enclose a stamped, self-addressed envelope.