I don't know what to do and I feel like self harming?? please help :(?

okay, so I was with my best friend, and he kissed me while I was with in a relationship with someone else. So i broke up with him and got with my best friend. everything was going great, then he messaged me and said that he liked me ASWELL as someone else, and i don't know what to do, I just feel like breaking down into tears or harming myself :(