Extremely confusing relationship issues. (long)?

Alright, so back in November I met this guy named Tristan at this party I went to. When I met him, we had this weird connection that we both felt (really hard to explain) and immediately hit it off. Halfway into our first conversation he told me he had a baby and was still with the girl. He went on explaining how he was unhappy because she pretty much treats him like trash (which I ended up seeing in the same night.) We kept talking for a long time and grew closer and closer. Everything felt extremely right with him and I fell hard. She continued treating him badly so he ended up leaving her for me. Our relationship was amazing. We never wanted to spend a day apart. He started seeing his daughter less and less because he didn't have a car and in order for him to see his daughter Angela (his ex) would have to bring her over and she didn't much because she was still really pissed off at him. Eventually he started missing her to the point of tears, and it killed me to see that. After about a month, he cheated on me with Angela because he said it was the only way she would let him see his daughter. (this is not a lie, I know for a fact how this woman is.) He swore he would never do that again and begged me not to leave, so I didn't. I felt like I was really falling in love with him. A while later, he ended up leaving me for her because he said it was best for his daughter, which is understandable because she needs her daddy. We kept seeing eachother on and off and Angela eventually convinced him to marry her. (or threatened, I'm not too sure...) He still goes behind her back and talks to me, sleeps with me, etc because he says he loves me. Just last night he was saying things like, "Why did I marry her?" and "What have I gotten myself into with her?". I don't know what to do because it seems impossible for me to give him up, but he's married to another woman now. I need really good advice, please.