How do I free myself from this the torment of this jelous provoking situation?

I am seeing this guy for a month now but have known for two years. I didn't evaluate the situation before getting ually involved with him and realize I am in a bit of a bind because of it. He has asked me to be his girlfriend and such. I explained I would first think of what I truly wanted out of it before saying yes. Since then we have continued to see each other. I have become repulsed by some things, physically ill by others and now frozen by the things I have observed in his behavior. I think he is selfish, immature and a threat to my well being. My body was the first indicator of "somethings wrong". He has girlfriend, and is quite involved and active with some of them. Meaning they do things together etc. We had the discussion at the beginning and he has said he will change whatever needs to be changed for me. That even meant friend girls getting in the way. The problem is I stay with him to only find that his gym buddy "girlf friend" is still taking showers at his house. I can't think straight. I usually just turn the other way if a man tries to make me jelous and quickly lose interest. In this case its different because of the audacity of him to do this or allow it or condone it or to even find any reasoning at all that it is okay. He is 10yrs older than me and he is insulting my intelligence etc. I am so upset about it I can hardly function and at this point dont know what to do to free myself. I already told him that this situation does not work for me, period and that I will not interfere with his life style. I don't think its over,, I dont think he really gets it and im infuriated. I want it to be over. I want to feel empowered but he is coming back with " I want whatever you want" and so I dont know what to do. I need some instructions. I feel violated, Im sick because of it. I am able to talk with him but I can hardly stomach anymore. To put an instructial pamphlet in front of him only makes me out to be controlling, not to mention exhausting...I dont want to be his mother. In fact I just want to rewind and start over.