Help!

I have been in love with my family friend ever since we were young (he is 17 now and I am 16). I was going to tell him but then he recently got his first girlfriend. Now all I think about is sex with him and it is overwhelming how strongly I feel. Of course in my dreams I would tell him and we would ride away into the sunset but in reality I think he will turn me down. So should I tell him, or just have him graduate this year and not be able to confess my true feelings. HELP ME.