How to deal with an ex...who still wants to be friends...

When I was 10 years old I met the guy I just recently broke up with. Grew up with him and knew his family really well. We lost touch and I heard that he got married when he was 18. In July of last year he contacted me on facebook and we started talking again. He had just split from his wife in June due to her cheating on him after 7 years of marriage. They weren't seperated but 3 weeks when we started dating. Things were really good, until we moved into a house 3 weeks after dating. We had such a history that things just seemed natural to move in. After moving in, and learning more of my past (let's just say I was frivolous in college and I've been with more people than he has) he started realizing he couldn't deal with my past. I was still friends with some guys that I had been with in the past and was still getting texts and phone calls from them and I wasn't telling him about it. He got upset(and rightfully so) and I changed my phone number so people couldn't call in order to make him more secure. Then, he decided he wanted to go :get his numbers up: and started talking to people we went to high school with. He even went to dinner with one girl who I was very good friends with. Now we've broken up...for about a week at this point. I saw him on monday (and today is saturday) and I didn't speak to him until wednesday. He came to the house to give me some stuff and we went to dinner and talked. Then things progressed and we ended up sleeping together. He came to my house and watched a movie and said he wanted me to come over on thursday. Around noon on thursday he said i shouldn't come over, yet continued to text me. I heard from him around 5pm and then not again til 930, in which he texted me for 2 hours trying to get me to come over...but I thought something was fishy, so I didn't. Then yesterday we hung out pretty much the whole day and went to dinner last night together, then I went to his house and stayed the night. Again things progressed and I didn't get home til 230 this afternoon. While I was at his house I found a phone call from around noon that was from this girl that he had dinner with awhile back...she called right before he sent that text message telling me not to come over. Then I found a picture taken that night of them 2 together. Now I know I shouldn't have been looking, however being as we are still sleeping together and still wanting to be together and we still have feelings for each other...I just needed to know the truth. I just kinda felt like I was his backup plan that night and I just kinda need to know his intentions. I want to be his friend, and he wants to be mine, but I just don't know how that's going to be possible with him dating this other girl. I wanna ask how long they've been going out, but I don't want him to know I snooped...I just need some advice on how to handle this situation and what t even say to him...