Friends with benefits failure

This summer I recently became intimate with my guy bf that I’ve known since I was young he broke up with gf and we began to talk one thing led to another then boom.

I told him if he was still talking to his ex in anyway this was over not only did he lie to me about them being over they are still dating and he told her I wouldn’t leave him alone and wanted to give him head. Everything in me wants to curse him tf out but at this point I don’t want to give him anymore of my energy any advice on how I should handle this situation?

P.s don’t sleep with your guy best friend it never works out at end you’ll realize sooner or later