I read this thread in one sitting tonight, but I was being quiet since I didn't think I had much to contribute. But you asked, so . . . .the answer is: I don't know what my advice would be.
I don't feel like I know your situation very well. When you're up, you're WAY UP. When you're down, you're way down. You have every reason to be WAY DOWN when you're upset with him, so don't get me wrong. I just don't know if I understand the marriage from reading about the last few days, with your spirit soaring while he was gone at the thought of how great things would be, followed by his second night home and your drop to crestfallen as you talked about the lie he told you (well, the lie you suspect) about this other woman.
Personally, I'm tempted to advise you to talk to him about it again. We talk a lot about boundaries here. It might make sense to let him know that this woman is just off limits. That you know he might have a perfectly innocent friendship with her, but for the sake of yourself and the marriage, he's going to have to let her go.
I understand the concept of choosing your battles--the term in special education where I work is "Choosing the hill you're willing to die on." But I'd be concerned that the boundaries will move--tolerate him buying another woman underwear in secret, and it's not hard to imagine that there's not a lot further he can go without really ruining your marriage--again.
But I would never have expected anyone to come back from the affair you described, so you've already done the impossible, and that makes you mighty. Take everybody's advice with a grain of salt and don't make yourself crazy either way. If your husband is as reformed as you say he is, I don't think it will be asking a lot for him to understand that a guy who has cheated as flagrantly as he did gives up the benefit of the doubt. He needs to be above reproach.
Nobody will think less of you either way, so do what you think is right.
Before I married my wife, when we weren't "officially" engaged but we both knew that was coming, I worked at a summer camp. One of the other counselors was a beautiful girl, and she's the only girl who ever tempted me to push the boundaries of my relationship with my wife. I can't even remember her name now, although I can picture her face. Nothing physical happened; we had long talks, we played a little too flirtatiously in the water at the beach, that sort of thing. I never pushed it far enough to find out how she really felt, but I knew how I felt--if I'd been single, there would have been no doubt.
But in the end, I knew I couldn't have them both. I made a choice. It was the right choice. I chose the girl who loved me and wanted to share her life with me over the girl who flirted with me.
Does your husband understand that he can't have you both? If he does, maybe you really are better off letting it go. If he doesn't, I don't see how you can.
