You poor thing. This sounds so familiar. We are only 2, 3 weeks on. my husband says didnt feel brill about himself either and didn't know what he wanted.
They too were texting each other and meeting up, usually when i was working. She too was our next door neighbour until we moved house in Sept and she started being in our house more and more, and stupid me thought she was infatuated with me and the kids but it wasn't. He said he loved her but i think it was just an escapism where he could forget his responsibilities at home and work.
Now i have no doubt that he wants me and the kids. but if your going to get through this your going to have to talk, talk, talk.
Get some counselling, for you and for both of you.
It's not just us it effects is it. its family, friends, colleagues.
Wish i could give you big hugs. But only you can decide whether you want him or not, but for me i can't throw away 14 years of marriage without a fight, and if i'm honest there have always been things that we need to work on in our marriage.
All the best and keep talking mumsnet has been a godsend to me over the last few weeks