He says he wants his family back

Back ground story....so we broke up 9 months ago. After we broke up a month later he started going with his coworkers and started messing around with other girls. Which I never started messing with other guys just focusing on myself and my son. But I have meet this other guy he really likes me we just been on dates. He gets his son whenever he wants but he chooses to get him every other weekend. This girl met his family and my son. So I figured they were serious. They went on trips together and everything. But they always been on and off. He’s always been messing around with other girls including her. I found out he dumped her. He is on child support because he hasn’t been there when I was pregnant. Am I in the wrong for this? I would love our family back one day but I’m not sure if he’s just trying to play me to get child support or if he really wants to work this out. I’m a very sweet girl and I’ve been with him for 4 years. I did slap him because I was hurt I know it was completely wrong but I’ve never cheated on him or anything Should I just back off .....I do work I make 13an hour he makes 20. His child support takes care of daycare which is 550 a month I tell him this all the time but he seems like he just don’t care. I just feel like if he really wanted to work it out he wouldn’t mention child support and after all of this he seriously asked for me to have sex with him.