What do I do about my exbf problem?

My exbf lied to me, our whole relationship was based on a lie. He "cheated" on me and the reason for the quotes is because during our relationship he was talking to another girl. I think, personally, thats cheating. He's a lier and a cheater. When he broke up with me he told me he was movin and I'm not exactly sure if that's true or not but I know for a fact that he lied. I just don't know what to do anymore. My sleeping and eating is totally off wack because of this and it's effecting me way to much. I've been trying to keep my mind occupied and it's worked a little but the other night I gave in and cried till I couldn't breath anymore. I just don't know what to do anymore and I'm going to have to see him at school. How should I handle this? I want to show him how much he affected me but I want to b able to get over this. Please please help :/