Assistance

My ex and I had a car together. I got into an accident and we owe 1000$ on the car. When we were together he wouldn’t let me have login info to anything and I would just give him money. “Loving boyfriend “ he was abusive so I had to leave. Realized after having a child with him. We aren’t together anymore and now he is trying to make my life hell. He is diminishing my credit not paying the bill and he’s withholding the account info. I hate him so much. Is there a way I can get this information or something? Like anything at all. It’s not fair to me and my child and I need to just take his childish ass to court. Trying to be cordial with him and he continues with being shitty to me because I don’t wanna keep dealing with his shit. Any advice would help.