First of all, I'm not sure what you're referring to in your post, but I'm guessing.... You don't say what your age was at the time of these I'll-show-you-mine-if-you'll-show-me-yours encounters. If you were roughly the same age and the other guy was not significantly older, that's one thing. If, on the other hand, you were a little kid and a teenager or adult was fondling you (whether or not you found it pleasurable), then in my opinion this would fall into the category of abuse.
Just because sexual encounters are not violent doesn't mean that they're not abusive. Covert and pleasurable sexual acts are sometimes not viewed by the child as abuse initially, and this may be the situation for you. My intuition tells me that if there were inappropriate/abusive sexual encounters then they DID have an affect on you. And perhaps this is why you have come to this discussion forum.
Probably the greatest damage in instances of sexual abuse is the psychological and emotional damage which distorts the youngster's reality, sexual identity, and the individual's ability to establish and maintain intimate relationships. (My wish for you would be that you could make the determination for yourself that, in fact, whatever happened to you was simply childhood curiosity and was not inapproriate and abusive.)
You don't have to know any answers right now....you just need to ask the questions. What you need to be knowing will surface in its own time. If you want to speed up the process, you may wish to think about working with a therapist.
Good luck, Buster.... If you need continued support and encouragement, this is one place where you'll find it in large measure.