What can you do to get your mind off of a heartache or painful memory?

about a month ago, i caught my bf cheating on me... and it wasnt something I would have wanted to see. he was kissing the school tramp, and i broke up with him right then and there. and he didnt even say anything. I feel so alone and hurt. I dont see any reason to try, or any reason to look for the right guy. why do guys have to be the way they are? am i really that bad of a gf that he goes somewhere else? god. i hate this