I'm glad to be of help! Your sitch seems to be an abbreviated version of mine.
If you read on MLC, the first two stages which are Denial and Anger are usually undetectable. These are the times when the seeds of discontent are sown, when the MLC'er starts feeling that there should be more to life than what they have, when they start seeing their spouses as the cause of some (or all) of their discontent, their depression.
It is when the MLC'er goes into Replay where it becomes a crisis, because that is when they put into action whatever it is - they either have an affair, or leave (attempt to leave) the family. They feel the overwhelming need to escape.
In my sitch, I think my H was in the first two stages for as long as maybe 3 or 4 years. He seemed depressed, and his affections for me was gradually waning. We had fights, and I myself felt like leaving. I think I made it really go down by being a contentious wife, demanding, controlling. I reacted to his depression and hi pulling away by withdrawing as well. maybe I had my own MLC - I even threatened to leave him 4 times during that period!
Replay happens I think when there is an opportunity. In my case, my H met the OW while doing work abroad, and he helped her get a post doc in the USA. The OW, newly D'd herself definitely was also looking for an emotional prop, and two wounded people - what else can happen? I think my H's emotional involvement with the OW is rather deep, and it is hard for him to let go and forget.
Perhaps your H's wasn't that intense.
Whatever it is..... since you are here to save your M, and it looks like it is going in the right direction, just keep DBing - work hard on your changes and on living the DB principles as you have not had much time to really incorporate them into yourself, so you might have to be extra watchful. Count your blessings - you are in so much a better place than many here.... what I'm worried about is that both of you might not yet have fully learned your lessons, but maybe you can keep doing that in at atmosphere of peace and trust (that will be a new one here!)
I'd encourage you to keep reading relationship books - read "How to improve your marriage without talking about it" - I really found that helpful - by Stosny and Love, Reading the "Love Dare" also helped me understand what unconditional love is and how to forgive and let go. There are a lot of others which perhaps you two can read together - "not just friends" I think is a good one (haven't read that yet).
Thinking about the EA will just make you resentful and angry.
Look into your future together, concentrate on that, and don't look back. It pains your H as well, that's his punishment, when he thinks of how he hurt you. Make him thankful and happy by being the best wife and person that you can be, and by being strong for him as he is still finding his way, and may well be for the next few months.
((((Hugs)))
Me:49 H:45 D:12 M:14 T:18 Bomb: 6/26/10 EA: 9/3/10, fizzled out slowly, now ??? 11/5/11 Retrouvaille Finally piecing.... Its peaceful at last, but we got a looong way to go