S, Step back and take a huge breath. The situation will not be fixed in a day, a week or a month...it's going to take some time and he's the only one that can fix this situation. You didn't break him, therefore, you can't fix him. He's got a lot of "stuff" to work out for himself.
You, on the other hand, need to keep your focus on you and your children. It's hard, but your family needs you now more than ever. Do not discuss the ow w/him, do not bring up divorce unless you want one and above all else, do not bring up relationship talk at this time. Your h is looking at you and the relationship as the ball and chain that are dragging him down to the level he's at now with dissatisfaction. You do not need to provide him w/any additional fuel to his fire.
It's a long, hard road, but you can get to the other side...but you must understand that nagging, checking up on him, etc., will not get you there. You are not his mother and you to get away from this type of behavior. You need to take care of yourself. We all have been where you are today and trust me, we all have tried things that we thought would help and they didn't. So, please listen to the posters and know that we have gone before you and have experienced the same thoughts/feels, etc., that you have.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.