I'm sorry you are struggling 9iron.
As you are married you likely know that most women need to feel emotionally intimate before they want to be physically intimate. Not all women but many. Men don't seem to be wired this way for the most part.
I have no advice other than be honest with her. My ex cheated on me and one of the reasons he stated to someone else was that he was lonely and I should have known that. I woud rather have known what he was thinking prior to what he acted upon.