Im think Im frigid how can I change?

I'm 15 and Ive only kissed. But that's not why I think Im frigid, Ive kissed about 4 boys, and been felt up but only over my top, but that's not why I think I am either. It just all my mates have done something else and I no it ain't a competition but its not like i never get the opportunity, I just feel I wont do something right and look stupid, Im not talking about sex, like other stuff, and I no ill never no till I try but I cant get over that feeling, and well yeah how can I change?