SS, here's the thing. He made choices. You weren't the cause of his choices. You say he wasn't bad all the time. No one is any thing all the time. That doesn't mean what happened didn't happen or that it was your fault.
Do see an IC? Can you? Are there support groups in your area? He's been working on you for all the years you've been together. It's going to take a long time for you to turn that around.
Your H's choice of OW has nothing to do with you.
Value yourself. Do something just for you everyday. Enjoy and value your kids.
Me 57/H 58 M36 S 2.5yrs R 12/13
Let me give up the need to know why things happen as they do. I will never know and constant wondering is constant suffering. Caroline Myss