IT WILL GET BETTER! I wish I could be there in person to wrap my arms around you and tell you this!
My marriage didn't last as long as yours and we didn't have children together, but like you, my ex flipped a switch... he loved me until he decided not to anymore. He didn't beg and plead. He didn't promise to cut off APs. He didn't even delete any messages or change any of his passwords to cover his tracks, which is the first thing most busted WSs seem to do after they get caught and are trying to cover their asses. When I told him I wanted to separate, his response was "Well how am I supposed to pay rent on this place with just my salary?" The only time he cried was when his friends and family members called him after I left to see how he was doing and he needed to score sympathy points; meanwhile, he emailed his AP about how "relieved" he was that I was gone. You can only imagine how crushed I was to read that... I had this fantasy that he came home to an empty apartment and the shock would make him realize how much he loved me and needed to win me back.
Eight years later, I find myself happily remarried, we own a house (which wasn't possible before because of my ex's non-existent credit), and we have children (which my ex kept putting off, probably because of his affairs). My career has also taken off because I'm actually able to focus on my job instead of how fucked-up my marriage is. I got my good looks back because I'm no longer binge eating or breaking out in hives because of the stress.
The best advice I got was not to think about the future, but to try to get through 1 hour. I know it seems like nothing, but trying to get through one hour is much more manageable then the rest of your life. And if you get through 1 hour each day without ruminating about him or the affair, then do something to reward yourself. Eventually, 1 hour turns into 2, which turns into 3, etc... until you've gotten through an entire day without even realizing it!
The only caveat is that you can't expect the process to be linear. I would go for weeks in a perfect state of meh until something triggered me (like seeing his favorite movie pop up on the screen while channel surfing) that would send me spiraling. But the good thing is that, over time, I recovery from these bouts became quicker and easier.
Please, please, please do not give up on yourself! Give yourself compassion and grace, as if you were your own best friend.
As an aside, the one thing I noticed in your post is that you don't mention friends, family, or loved ones. Do you have any people in real-life to talk to and lean on for advice and comfort? While I'm sure you don't want to be an emotional burden on anyone, it is important to have confidants as well as people who can take you outside of your own head. Regardless, please know that we're hear for you and we care.
BW, age 40
Divorced WH in 2015; now happily remarried to a great guy
I edit my comments a lot for spelling, grammar, typos, etc.