He Wanted to Commit Then Dumped Me?

My guy and I have been casually dating for a year now. We are co-workers. He says he loves me and I love him, but most of the time he has been seeing two other women as well; one of them is also a co-worker. At first I tried to be okay with it and go on dates with other guys, but recently I realized that I did not want to be an option to him anymore. I did not like 'sharing' him. And so I told him I couldn't handle things the way they were; he's always saying he loves me very much and can't be without me. I told him I wanted to be exclusive. He said he didn't want to be, even though he had ended things with one of the women and was planning to with the other. I said, okay, fine, good luck with life.

A few days later, he approached me and said he had thought and knew what he wanted, he wanted to be exclusive with me. I was still wary, especially given that he said, in regard to his break-up with the second woman, the co-worker, that it would "occur at the proper time." What did that mean? He said he did not like big blow-up confrontational breakups, but preferred slow withdrawals as it hurt both sides less. And he said he would end things with her in no more than two months. He has also said, since he started seeing her, that there was no future there, that he didn't see her as long-term, and didn't trust her. Naturally I was still skeptical and kept up my guard.

I should also add, right before he said he wanted to commit to me, that I met his kids. It was very casual, but they absolutely loved me and kept asking him when I could come over again after our first visit together.

This past week, I had some time off from work and so he asked if I would stay with him a few days and could play with the kids. I did and thought everything was fine, aside from a misunderstanding that we cleared up that night (misunderstanding being he had some work to do online and told me it would only take a few minutes when in actuality it took several hours, and I got annoyed with him).

Day after the misunderstanding, he had to go to work. He was distant most of the day and I asked him what was going on. He said he wasn't sure if we were compatible in some areas, and he thought I had needs he couldn't meet. Out of the blue, after saying for weeks on end he wanted to commit and be with me and seeing how well his kids and I got along. I asked him to explain and he wouldn't. When he got home, he said he was just tired and would explain the following day. We had a nice evening in spite of this.

Next day, same thing happened-distance. When he got home from work, he said he had some work to do online, and this time I was aware it would take some time and so I kept to myself. I wanted to ask him to explain the previous day, but did not want to fight, either. I thought things were peaceful.

Day after, he seemed distant when leaving for work. I texted him later in the day to ask what was going on. He said he thought our needs and temperaments were out of sync and that we weren't compatible and that we should end things. He said he was sad and his heart was heavy, and he promised he was not ending things to be with someone else (read: co-worker).

The next day, we had to work together. I had planned to be calm and not say anything, but when I saw him and the co-worker together (I didn't actually see them kissing, but they both acted so flustered when they saw me I feel sure they were doing such) I made a snarky remark about him having a good morning. He promptly told me to shut up and we went at it.

In addition to the previous remarks (not compatible), he said all week that I had been at this house he had felt tense and thought I was unhappy, and that I stressed him out and it shouldn't have to be that way. He also said I wasn't as mature as he'd thought, and I asked him how he went from wanting commitment to incompatibility and if he'd had a problem, why didn't he say something earlier in the week. He didn't exactly explain it too well. He said he had hoped things were going to work out, but he didn't think they would.

For the sake of professionalism, he said we could talk more later and I agreed since we were both at work. We stuck to neutral conversation the rest of the day and when I asked him when we could talk, he said the next time we worked together. I could ask questions, he said. I have not seen or heard from him since.

We are supposed to see/work together/talk in a few days. My question is, how could he go from wanting to commit to suddenly dumping me and blaming me for it all? He flat out said he didn't let just anyone spend time with his kids, that that should have told me he was serious about things. So if that's true, how could he so quickly go from that mindset and wanting me to distance and saying we're incompatible?