Co parenting

Alright so when I was 6 months pregnant the father of my child cheated on me with his now girlfriend are son is now 18 months and she and I just can’t seem to get along I’ve tried but she keeps telling me that I have to involve her in the decision I make for my child because apparently my baby dad leaves my child with her while he goes hang out with his friends 24/7 I thought he took our child to spend time with him but turns out he only spends a hour with him and on top of all this they both decided it be a good idea to Pierce our sons ears without my knowledge or permission because I got our son a hair cut without my baby dads permission even though I talk to him about it and he told me he was gonna take him to do it and never did so I decided to. I’m just here because I don’t know what to do anymore this girl disrespects me, tells me that I can’t make plans or decisions for my child without including them I’ve told my baby dad repeatedly that for I don’t want to talk to her or include her in the decision I make for my son and he still lets her continue to do the same shit and I just feel like I shouldn’t let talk my son anymore because it’s bad enough he cheated on me while I was pregnant which believe I’m over it at this point but the fact that he has this girl raising our son not even helping him she been doing it by herself and her two kids, he takes our son whenever he feels like it and returns him days later. It just hurts me that all this time I thought he was spending time with our son turns out he’s just been leaving him with her to hang out, not work or study like I do every day but hang out. I’ve tried talking to him arguing with him I just can’t take it anymore and feel like I’m gonna have a break down pls someone help me out wat do I do at this point 🤦🏻‍♀️🤦🏻‍♀️🤦🏻‍♀️🥺🥺