who regrets their ex

My ex is my number one regret. The only good thing that ever came out of our relationship was our son. He is putting me through hell and I find myself hating him for it. He complains about everything, ESPECIALLY when it comes to giving me money for my son. I have been out of work since June and he has been giving me such hell over it. Sometimes I just want to cry. He is verbally abusive and I just don't know how to handle him or what to do. I did apply for cs. And I was thinking of getting a restraining order but I don't want to keep him from our son...though he doesn't really see him anyway. What to do?