How to get over a straight boy crush.

Okay, so I've had this crush on this boy well let's refer to him as A, well A and I met during 9th grade in biology class. I didn't think much of him the first day of that class but he started talking to me and I thought to myself "Wow a friend, okay" and then.. I don't know I started finding him attractive and more until the point where I knew I had a crush on A. I remember thinking to myself "Oh.. Fuck no..." And so as the year went on by I became very good friends with him, I then told him about my sexuality and he seemed cool with it I guess he's one of those rare straight guys. Anyways we only had 2 classes together which sucked, fast forward 2 years into my junior year of high school and that's when I notice a difference in the way he talked to me and stared. I occasionally caught him staring at me during 2nd period and I turned awfully red. In our winter break that year we faded, we didn't talk as much anymore and he slowly started disappearing as a friend. My feelings grew more stronger as I didn't interact with him. I'm in my senior year in high school now and he's still here. I see him in the hallways sometimes and he waves and smiles at me. I wave back smiling, and it's killing me inside. I know that we have no future together as a couple I'm just wondering how do I get over him? I just can't deal with this anymore. Please help.