I am sorry you are here and suffering.
It's late and I don't have much to offer, except...choose the frying pan.
Seriously though, your husband probably does have bad coping skills and low self esteem, who knows what else. Thats why IC is so important. He needs to find out what made it ok for him to escape to an A.
It isn't about you, and you may be his world. He more than likely has the ability to compartmentalize (to separate something into parts and not allow those parts to mix together)
His life with you is stored neatly away while he goes out and leads his A life, when he returns the A goes into his little box, tucked quietly where it wont be found or be able to bother his conscience. It's a way many cheaters cope.
Unfortunately many WS's dont think about their spouses and families when entering into an A. They don't think they will get caught or they have hidden the feelings away.
It isn't about you, at all.