I need to break the tie he has over me

I'm looking for advice on how to go no contact when you have a 2 year old child together. I've already blocked him on all socials but i need to keep in touch via phone for our child. I don't like his mother and want her to have as little to do with my child as possible (that's for a whole other post) so I don't want to do things via her. I'd like to never talk to him again if I had my way so I'm stuck. How do I coparent and cut contact at the same time?

This man knows my weaknesses and even though he has a new girlfriend now, he still messages me. Not sexually but friendly, as far as I'm concerned he shouldnt even be doing that because we are exes, not friends! Maybe he feels bad for the way he treated me idk and idc, but I'm sure his girlfriend doesn't even know he messages me. Either way I need to heal and need him out of my head, out of my heart and out of my life.