Getting over a crush

I just "graduated" middle school and we had a dance after the ceremony to celebrate. The whole year I thought this guy liked me and eventually I developed a crush on him. He's super nice and cute. He would sit next to me in class when he could. He would talk to me during class and laugh when I said something funny. Then at the dance he asked a different girl to dance with him. (That's sort of how my school like asks someone out). Now that we are both going to separate high schools we won't see each other anymore. The problem is I just can't get him out if my head. He's literally the only thing I think about. Should I tell him how I feel? How do I find someone else?