What's the best way to mend a broken heart?

My boyfriend of nine months broke up with me tonight in the most f*cked up way! We had our Sadie Hawkins dance tonight and I didn't want to go and neither did he. But he told me one girl (who wasn't me) asked him and he said no because he was with me. (also the girl who asked was his ex girlfriend) but, little did I know he went with her anyway, and I had to find out through a text message from him that he went and I just asked him why didn't he tell me and he said he didn't want me to be mad at him. of course it made me more mad after wards! I didn't feel like arguing with him so I just dropped the situation. But he texted me a few minutes later saying he thinks we should break up because he thinks he's fallen in love with her again. It hurt so bad all i texted back to him was bye. I seriously don't know how to handle this one. I know this is long but how can I get over this?