I predict you'll get a lot of responses on here about how it'll never work. Mainly from people who didn't want to or couldn't make it work for them. That's their experience. What you are going through is yours. Just something to bear in mind.
I've been through similar - affair last Spring, separated, started a divorce, stalled the divorce, reconciled, cancelled the divorce, now together and with a baby added into the mix. It's been a roller coaster of a year, and not one I'd re-live in a hurry.
The questions you need to ask yourself:
Have you cleared up all the old hurt, misunderstandings and issues in your marriage? We all have them. Are there still things that bother you that have been swept under the carpet?
Why have you stayed? Dig deep and be honest. Why?
Has he changed? Really fundamentally changed? Anyone can say sorry. It means fk all unless they follow up with actions?
Do you know you'd be ok on your own or are you clinging on because the future seems too frightening if you don't?
What does he do when you are having a 'bad day'? I still have bad days! Show me someone in our position who doesn't and I'll show you someone hiding from reality.
If you can answer those and the answers suggest you are happy, then I reckon you can make it work.
As for the pain and the sorrow, well no, it doesn't go. I should keep off the relationships board really because reading other women's hurt exposes my own. But, in my case it has faded to bearable, due to the simple fact my DH does absolutely everything he possibly can to alleviate it. It doesn't sweet talk, he acts. I largely ignore words as he lied with the best of them at the time. I judge him on his actions.
I hope you make it work in whatever way is best for you. Never settle for second best. Follow your heart and be happy. That might be with him, or it might not.... but never settle.