Ex boyfriend problems..

So long story short I broke up with who's now my ex boyfriend like 5 months ago?? I think, this morning he messaged me and was like ooooh guess who I'm chatting up now and I was like oh yeah who and he said her name... this bitch is my childhood friend, and she knows exactly who I am to, and tbh I dont think he should go there and nor should she, it's not as bad as if he was getting ins with my current best friend but a childhood one isn't the flashiest option either, so anyway I asked him, why is he telling me this and he said he didn't know just because, pathetic reason, real reason was is to fuck me off and it worked, I cried all morning because I just felt beat and unwanted, I should be over him by now and I am, it's jus the keeps doing shit like this and its holding me back from moving on, thoughts?