How do I move on when he's all I've ever thought about?

So I met this guy 4 years ago. I had just moved to a new school and he was the only person I even recognized. We became friends almost immediately. I kind of fell in love with him almost immediately. But he had a girlfriend. Eventually they broke up. We almost dated, but he had second thoughts. I was devastated, but I told myself eventually I would move on. (I was only 13 at the time) It turns out I didn't, every time I even got close he would ask to hang out and I would pretty much be defenseless. At the start of my freshmen year things looked really promising, we even walked across town and it ended in our first kiss. But nothing came out of that and I tried yet again to move on only this time I didn't even acknowledge his existence. This didn't work. We dated at the end of my freshmen year and he broke up with me. I know it's time to move on, but it's just a habit for me to think about him now. I really am in love with him, but it doesn't seem like I even meant anything to him ever. To top it all off, we have to see each other because we're both in band, contest speech, and only a year apart in school. I'm trying to get myself to like other guys, but all I really want is him. I've told him all this and he just doesn't care. How do I move on when I can't stop thinking about him. How do I move on when he's all I've ever known?