I'm in the same situation. I began a relationship with my colleague more than a year ago and it went on and off several times during that year. But he was really in doubt about his kids. He told his girlfriend rather quickly that he was in love with someone else, that it was someone from work. So, as every woman would, she quickly found out who it was, me. She started to threaten me and I understood her partly... So we parted but after 2 months we missed each other so badly so we started meeting again. During the summer of 2012 the situation at his home got so out of hand that he really wanted to leave her but he was still doubting for the kids. They were in therapy, but that didn't work (according to me they really didn't take that seriously as they stopped this after 2 months, and she believes everything that went bad in their relationship is his fault, even if it was already not going well before he met me) He said I was the love of his life and he wanted to be with me... blablabla ... And when she threatened him again to take away the kids he decided to stay with her anyway. That, in a way shocked me, because he already asked me several times if was going to be there for him and we had talked about a future.
So, that was it. I was devastated, because what we had was a really deep and emotional bond and all of this was gone in a moment. I have thought of leaving work, but I can't because it's my first job that I really like (I live in Europe) and a lot of my colleagues are also friends. I really wanted to talk about it and how he good just change his mind setting 180° and shortly after we broke up we met a couple of times just to talk this through and figure out how we were going to do this at work as no one wants to leave. So we found a good consensus. But I believe some three months ago sth happened at his home and all of sudden we was totally distant and he acted like nothing ever happened, like we never got along even. He was like a perfect stranger. Again this was really hard for me. Because what I mainly feel in this situation is that he always decided how things went and go and I just have to accept it.
During all this time (and for much longer, actually) I'm seeing a therapist who helps me cope with this situation. After my MM's last change, I decided to change my own mind setting and focus on myself. If someone doesn't want to be in my life then I shouldn't spend time on then as they are not worth it. This is really hard to live by, as I am an emotional person, but it helps. Also I have a good friend/colleague who knows about the whole situation and she's always been a good support through this whole time. We are now 6 months away and some days I really feel sad and on other days I am more in a "fighting" mood. When I feel so sad and I miss him too much I think about the fact that I can still meet someone new and have a nice new relationship, where he is in a situation where I don't think it would be so nice coming home. I don't think that she can ever trust him again and he must always feel guilty towards her.
I am angry with him because of how he treated me (he was also the one who made the first move). Also because now he barely talks to me, it's like I don't even exist. We had such a click. I know he does this because he made a click in his head that he has to focus on his family (I don't understand how you can just make a click of 180°, but also he is a man and I don't have kids so I don't know the impact of that).
On the other hand I knew he wasn't available and I still went along... because I was (and actually still am) in love. But I learnt from this situation. Luckily I also have good friends who support me and a loving family (mom and sisters).
My therapist says that for me the situation is harder as I am single and I have nothing to go to and he has his family.
I know I will get through this... but now I'm still curious if he regrets hurting me so much and if he misses me... But this I won't know.