Baby momma drama

So me and my girlfriend of two years together broke up about 3 weeks ago. I know we shouldn’t be together even though i know we both love each other.she the day we broke up started living with her ex bc her only friend in town happen to let him stay there.the whole time we were together she talked about how she hated him and SHE did these horrible things to him and so did he her.we have a baby boy together he’s 7 months old and live by myself and she’s already sleeping with a dude she claims she hated.But much worse is she’s starting act like he’s the father I’m not sure it it’s to get me jealous or what.i get to see him every holiday and he stays the night with me two times a week(days off work) but she’s told me how he’s took him to doctors appointments paid for his birth certificate and bought him Christmas presents now that idc about but she didn’t even ask me to come to appointments or pay for that which I would have done in a second . Just wondering what I should do from here I’m working on myself like going to gym and self care but I can’t stop thinking about it.