Major crush on my tennis coach?

alright...b4 i say anything im not some crazy slut. just to be clear here. i just have a BIGGGGG CRUSHHHH on my new tennis coach. he.is.so.hot. one problemo,im 15, a sophmore, and he is like early 20's. i live in south carolina, im just wondering if that is illegal. i dont know if he is attracted to me at all, but in my opinion he is, but i rlly cant tell if hes just being nice. i feel pathetic asking this haha but wat should i do? just let it go?