I think Michelle quotes someone as saying "if you don't have an affair with your spouse someone else will".
I do not know the exact details and how much your H has struggled with being faithful, but it is sometimes some simple void or thing that can make the person seek something outside that should or has been part of the M for years.
I think that the sex thing is great as well, who knows maybe he was looking for some of that and instead of communicating with you found someone else.
I struggle with the trust issue, did so yesterday as well. I felt that my W was out there with the OM, don't know why. Then we had a very loving and real moment last night so I was probably wrong. That will take time.
Another marriage guru said that after an affair the marriage will change so one has to learn how to deal with that, it is so true, and we have not reached that point yet, our wedding song was Randy Travis forever and ever amen, and it ends, "if you wonder how long I will be faithful, let me tell you again, I am gonna love you forever and ever amen,
My W knows this and they always play it at our social functions so it is hard for my W,