Co Parenting

Idk what else to do I co parent with my sons dad it been extremely hard because for the last 3 weeks or son my son has been acting out in school following the wrong child and he started to be disrespectful to me , I would call his dad to you know to help me correct his behavior because for one I live in a shelter it’s so much I can do but redirect him but his dad said I should have to correct him while he is over there with you . Then his gf some reason always find away to interfere with are co parenting I don’t disrespect her at all and it’s like I’m tired at this point he constantly bashing me on Facebook not to mention my son has previously hard and seen them have intercourse I had talk to his dad about but yet it’s going on a third time and I said something again he denied it and said why you talk about my gf, I’m addressing you and her because now he thinks what he seen is okay and it’s not especially when he doing little things . Idk what to do I feel like I can’t win at times because he is a liar and constantly talk shit about me , I want to take him to court but I feel like is the gonna see where I’m coming from vs me living in a shelter . Help any advice please this really a cry for help !