Going crazy

I wonder if anyone has an opinion on this...if yes PLEASE share it with me! I have this "friend" who I've known for about three years. When I met him, I started falling in love with him but always had an uneasy feeling about him, and luckily I realized before it was too late that he was a player and at times fooling around with six women at the same time. Still, I was very fascinated by him for reasons that I can't go into now...so we decided to be friends. Well, actually, at that time I had this crazy idea that I should try something new so I asked him if he wanted to have sex with me once in a while, just whenever I felt like doing it. I thought that I was cool enough to do something like that, with no feelings involved and no strings attached. But other than that we really were just friends. It worked pretty well for a little while but then it got a little complicated when I started to become jealous of all his other women and constantly had to fight this feeling. Guess I'm not as "tough" as I thought I was but I couldn't do this without having feelings for him, and they grew more and more even though when I got to know him better and better I didn't really like what I saw. He is lazy, unreliable, controlling, a liar, a cheater, a megalomaniac, he uses other people and takes advantage of them - including me. In the meantime, all my friends told me to stop seeing him as they thought he had a bad influence on me and they were worried about me.
Anyway, this went on for a while until I left the country. The first few months were hell because I missed him like crazy, but it got better eventually and I swore to myself that I would NEVER become emotionally attached to him and let him screw with my mind again. 1 1/2 years later I came back and thought I was strong enough to face him and be around him without getting all emotional again and slide back into old habits. So I moved in with him as his room mate, which, believe it or not worked very well. The rule was no touching, no coming close. I had a great time and I thought I was really lucky to have a friend like him, and I thought everything was going great, but after a while he started making very ambiguous remarks and finally admitted to me that he would be in favor of starting our "sex buddy" habit again. The thing is that he had a steady girlfriend at the time. I told him no way and moved out, but it was already too late and we ended up in bed together. I'm SOO weak!!!
I know him quite well, and I have developed this absolutely pathetic sense of protection for him. He's a pig, and everything else I don't want a man to be, but he also has a soft side, and he's actually pretty damn insecure about himself. That's why he needs to have the big lifestyle, the cars and the women...He means a lot to me, and I'm miserable if I can't talk to him every day. It's a daily struggle between my brain and my heart, because reason tells me to stop seeing him and to get on with my life, because he will never change, and there's no future for him and me no matter what happens. I know him too well and I could never trust him, which I think is the basis of any relationship. At the moment, he makes me feel miserable 23 hours and 55 minutes every day, and I have to admit that the 5 minutes per day that he actually makes me feel good are not really worth it. But my heart really goes out to him, and I know for sure that he respects me and that in his own weird pathetic way he really loves me, and only the thought of loosing him makes me wanna cry.
I'm thinking, am I a masochist to want him still even though he treats women like shit? How can I think that I'm special to him only because he tells me so, and because he's honest to me and tells me about all his other women, while the other women don't have a clue? He does have a good heart deep down inside, but you have to dig VERY long and deep to find it. Officially, we're still "just friends". A lot of things have happened between him and me that I can't go into right now, but I'm now at a point where I'm saying I can't take this any more. Or am I just overreacting and he isn't really that bad? Tweet