Am I Dreaming About ?

Earlier this year I've been going to upstate NY to visit my cousin(I live in the city). I'm 15\sopre in h.s. and she's 14\freshman in h.s. We're best friends. She's really beautiful, and I've been dreaming about her naked & having with her. During the summer, I found out that we aren't related. Like, my uncle is my mom's brother and his wife had my cousin with another guy before they got married. Sometimes I feel really bad about it but at the same time I can't help it. Am I wrong?