Mentally hurting

Went to sign the papers to get my name off my lease, and decided to stop by my ex's work to tell him he needed to go in and do the same (for contextz he cheated on me with his coworker/boss). I parked and had a small sigh of relief thinking she wasn't working, but when I walked in I stared her dead in the face and froze. She knew exactly why I was there, and was trying to be nice to me. He invited me in the back so we could speak. Ended up being a 30 minuet conversation of him apologizing to me, telling me he never wanted it to end up like this, and told me I deserved better. I asked him if they were seeing each other, and he just said "we arent official but..." and I knew right then and there things have happened between them since I moved out 2 months ago; I just nodded my head with tears in my eyes. I was shaking so bad. He told me the group (our friends) missed me, and I'm always welcomed back. I just shook my head and said Icouldn't. He asked if it was because of him, and I just nodded. He still wants me in his life. Not right now obviously, but he said he wants us to stay friends and be able to sit in a room together and get along. I just cant believe he would say that when hes hooking up with the girl he cheated on his 6 year girlfriend with. He told me I had nothing to worry about, that he loved me, that he was going to marry me, that we were going to have kids and a house someday. I feel disgusted and so broken.

I left his work and just sat in the parking lot. I wasnt in a stable condition to drive. 10 minuets later he comes out and sees me, walking over and knocking on my window to check on me. He had to make a run to the post office. Soon as he left I drove home. I'm just so... broken...