Q.When I was 13 years old I became involved in four or five sexual episodes with my brother. He was 11; the initiation was mine. Much to my young brother's chagrin, I finally put an end to our activity.

I'm now 36 years old and feel quite anxious about this past sexual involvement, even though there was no intercourse involved. It makes me feel dirty and may be the cause (at least in part) of my inability to enjoy sex with my husband of 14 years. I see a clinical social worker regularly, but I'm too ashamed to bring this matter up.

Any information would be greatly appreciated. Do many children go through experiences like mine? Is it normal that it should still bother me as it does?

A.The conscience can be a terrible, troublesome thing.

It finally develops -- years after most parents assume it does -- and then spends the rest of its life chastising us for what happened before it took its full shape. It's time to tell it to be quiet.

Preteens and young teen-agers do all kinds of things that embarrass them later, and it's easy to see why.

From the moment of birth, a child's body, mind, psyche and spirit are growing, one sequential step at a time. Unfortunately, these stages don't always mesh. This is especially true when the hormones begin to stir, leaving parents -- and children -- to wrestle with the fallout.

There's the talking back and acting out, the sound and fury of young people who wish they could be on their own -- but are deathly afraid of the day when they will be. And there are nearly always some regrettable -- or at least indelible -- incidents to remind us that it takes a while for children to grow up.

Consider the unsupervised 12-year-old with the conscience of a 10-year-old, the body of a 14-year-old and a friend who's willing. She may be surprised to find herself pregnant.

Or there's the sobering experience of the 14-year-old caught shoplifting a candy bar or a dirty book. Between 11 and 15 a child may accept the invitation of a friend to try cigarettes or pot or liquor -- interludes parents seldom find out about. It's just as well.

Much of this behavior is forgotten by adulthood -- or at least accepted -- if it doesn't last very long or get too serious. The child either finds herself -- or her friends -- well supervised the next time she gets the urge to misbehave, or there are chores, homework or sports to push temptation away until her conscience finally catches up with her age.

A child, however, doesn't become moral overnight. Your own sexual experiments bear this out. You were the one who initiated the behavior, but you were also the one who stopped it. It wasn't that either of you ever thought your behavior was all right, but that neither of you were mature enough to say no to yourselves at first. This is because the conscience depends on the mind. You have to be able to think well in abstractions before you can consider the harm you might do to yourselves and to others.

It was unfortunate that it happened, but that was 23 years ago. Don't you think it's time to forgive yourself?

It's certainly time to talk with your therapist about it. When you do, she'll tell you that the episodes from your past are much more common than you thought, even between brother and sister. Unfortunately, you've been judging your 13-year-old behavior by the standards of an adult, and then expecting your therapist to do the same. This isn't fair.

A clinical social worker is trained to listen, to be sympathetic, to help you put your own jigsaw puzzle together, without making you feel guilty when the picture is askew. If her opinion means so much to you that you can't confide, tell her so and ask her to recommend another social worker -- perhaps one knowledgeable about sexual problems -- or to suggest a women's support group.

Talking about it will be your first step toward forgiveness and probably your first step toward a happier sex life.

You'll also want to do some reading. Although psychological problems may inhibit a small number of women, sex is basically a physiological experience. It's made much better by love and commitment, but a woman still must use the techniques that are right for her if she's going to enjoy it completely.

You may be interested in reading Sensual Pleasure by Eva L. Margolies (Avon, $2.95), a practical, very explicit, how-to advice book for women.

And to understand the 13-year-old you once were, get a copy of Growing Up With Sex by Richard Hettlinger (Continuum, $4.95). This guide for early teens, with its strong but realistic emphasis on values, will help you put your past into perspective.