How can I control my sex drive?

I'm 15 and I have a really dirty mind.(dont judge) I'm a virgin. And I think about my best guy friend (whom I have a crush on) all the time. I cant get him out of my head and I make myself wet and horny thinking about him. Only him tho, no one else. I try to get my mind off of it but I can't. Please help. (we've had phone sex with each other before)