Yea, I'd have to agree with Kaprika.
Even if you know sexual stuff, you don't tell adults that.
I don't know what's up with them, but they like to blow things out of proportion.
(Shrugs) I mean I'm 18, and they're still worried about me finding porn on the internet. Been there, done that. xD
I don't know of any way you can avoid getting into trouble now, sorry.
Just be truthful with your parents when they ask you about it, and tell them how you feel.