Need some HELP!!!!!!!!?

Ok my best friend told me that she likes my ex and i said that i still had feelings for him and the next day she goes out wit him.....three days p and my ex told me that he still loved me and misses me and he asked me back out and i said yes (of course) and the day we went back out i heard that he kissed some girl and i asked him about it and he demises the whole thing what should i do??