Open Question: Ladies who have been through a rocky relationship with your babies father.. Please answer kinda long.?

I going through this really bad relationship right now and I dont know how to deal with it.. Long story short Ive been with him for over 4 years and Im currently 18 weeks pregnant with his child (first) but he has a problem i believe he has an addiction problem to “cocaine” which i knew but i was too stupid to leave.. now i find out hes doing it again after i thought he had stopped for good.. and i finally told him to leave me alone for good i just dont need that bull right now specially now that im pregnant.. i could do this all on my own i work and have my family support.. should i let him be part of my babies life?? He works and has a good job should I also put child support on him ? i dont know i never thought i would go trough this ever!!! im so confussed in what to do for the best of my baby.. he does say hes going to be part of the babies life no matter what because its his child too.but I dont have anything to happen to my baby while hes under his care… I have no idea in what to do.. I just think hes being this way because hes still young (21) and im a little older (23) has anyone gone trough this before and what was the outcome.. as much as i want to believe he will change deep down i know he never will..