Am I in a abusive relationship?

Me and my bf fuss ALOT because he thinks I'm cheating. I am not cheating and have never cheated. When we first got together within a week of knowing each other we talked about 3some and I said well what about a open relationship. He felt so disrespected and let's says he won't let me forget I ask about that. He said he lost all his trust in me when I ask that. Mind you we was only going together about 2 weeks with 3 weeks knowing each other not like we been together for 3 years and I ask that! It was a dumb question but he feels I'm ALWAYS trying to fuck another man and even won't let me go by my friends bc he say I'm fucking my friends man. How disrespectful. Recently he started saying my pussy was loose when I moved back with my gmaw for school reason and for her to watch my son. It getting where we fuss all damn day and I'm emotional drain. Yesterday he blurted out I know you fucking someone else and I just left bc this topic then came up 100x. He grabs me while holding my son , I put him down bc he was being so aggressive. Next thing he sitting on top of me and would not let me get up. So I hit him and pushed him off me , he starts slapping me in back of my head and face refusing to get up. I'm crying for him to get off me and he said no , I said stop hitting me he going to say you hit me , ONLY for him to get up! I have so many bruises. I am to fuck him for him to leave me alone. This same solution happens all day ! The reason why I haven't left is bc he supports me with money and I have a son and I can't go without with a child! Jobs in my area are hard to find ! What to do ?