How to cut ties

I am in and up and down relationship with my sons father, it’s almost like he doesn’t want to let me go but does just enough to keep me in a space where I can only love him. I’m 8 months pregnant and I’ve been doing my hardest to keep no contact. He doesn’t do anything to support me or our son I’ve bought everything myself, picked his name out myself and I can’t depend on him I don’t see it being any different once he arrives. I want to write a closure message but can’t begin to find the words.