I'm pretty much where you are, just pregnant and without the affair (that I know of, anyway)... Not sure WHY I want to get back together with my H sometimes but I think it's the most important thing for the kids.
Sometimes I remember how much we used to love each other and have fun together, and I don't really want to find that with someone else.
The most useful aspect of DB'ing so far for me has been the "getting a life" - H said I became where I wasn't even a person anymore after having DD, and I'm finally seeing how I was missing out by not enjoying my friends, or buying myself things, or treating myself.
I've been enjoying the 180 too so far, because that confuses the hell out of H, and that makes it kind of fun for me.
Good luck! It's no fun to be here, but there are lots of great posters with wisdom and advice...
Me - 30, H - 32 T - 10, M - 6, D - 1 DD#1 - 4, DD#2 - 2 on/off OW 4/09 - sometime Summer 2010 (Told me about OW 4/10) Separated 6/11/09, divorced 8/4/10, trying again 9/2011