So you say that your H has only come to you and apologized one time?
This is one of those little idiocyndracies that he'd have to have a new person figure out.
So YOU did it--how quick was he to want things to be smoothed over? In other words, how hard did you have to work on him?
Clues to how to behave now....
You keep forgetting--there were things in your R that DID WORK. And you have a few more "tools" in your belt to how to make them work better in the future.
Don't think he would sleep with someone to "hurt" you--You have given it a go too (in your head). You were wanting to escape the pain. He may think it would have that affect as well. He has GOT to be lonely if there is no one else. Only his parents supporting him? How old is he??? It's got to be humiliating.