Numb - I know you are feeling really low and will not want to do many things but have you ensured you're financially secure etc. Please make sure all the bills, mortgage etc, are up to date for your sake and your children's sakes.
I know it's very hard thinking about things like that when your mind is occupied with him but it might be the last thing on his mind at the moment and I don't want you to come a cropper!
Don't be frightened of seeing a Solicitor. I know they cost money but I think the first half hour is free. Just because you see one, doesn't mean you've got to start divorce proceedings. Please make sure he is giving you enough maintenance.
Do you have any single or single again friends? Are you managing to find your own space? And time for you? I remember it was very hard passing the children over to him for the first time but then I got rather selfish about it and looked forward to 'me-time'. I began to meet new people (I met a lot of platonic friends after splitting with my ex. and these people remain good friends today). It is very hard venturing out as a single-again and that is why I am asking if you have any single friends.
I did a lot of positive things whilst I was single. I returned to college, went working behind a bar (which he'd banned me from doing whilst we were married) and became involved in charity work. I did have a few male friends but I didn't rush into meeting them straight away.
I'm now living with a wonderful DP whom I met on the Internet. We plan to marry when we can afford it and when we've both slimmed down
I see the ex twice a week when we are swopping the kids over. We get on quite well now. He married her and they now have a lovely son. DP has a son too and there have been occasions when all four children have played together for 10 minutes or so. There is no going back though. Even if the chance occured, I wouldn't dream of hurting my DP. I was telling Spook a couple of days ago that I accidently touched ex's hand at weekend and automatically withdrew my hand. I often wonder what it would have been like had nothing happened at all so it's true that I still mourn in a way our family as it was, however, I'm not attracted to him now. Does that make sense?
The 'letting go' is a slow but worthwhile process and you cannot put a time value on it. My advice is to try and find something positive that will occupy your mind in the meantime. Do you have parent(s) around you and/or sibling(s)? Where do you live?