From the perspective of this WAW (for whatever that's worth):
Tell her the truth. I don't see how that would be worse than pretending everything's all right when it's not. (That part of DBing I don't always agree with)
Of course, there's the risk that she won't respond in a loving manner but at least then she'll know how you really feel and you won't be torturing yourself with "what if I had told her how I really felt?"
And she can digest something sincere for a while instead of a happy face pasted on what she knows is an unhappy husband. Maybe she keeps asking because she senses the disconnect between your outer behavior and the feelings you project.
Personally, I would melt on the spot if my H expressed any of those kinds of things to me. (Provided that they were expressed in a self-respecting, non-whining or blaming manner, of course)
If my thinking was being clouded by an OM, it would take a lot longer to sink in. But believe me, it would register.
After I had confessed my EA (both episodes) to my H, he eventually told me that, although it hurt him terribly, he knew it was a symptom of a deeper problem in our M, that he knew I was a good person deep down and that that kind of behavior was not a true reflection of me as he knew me. That he could see the good in me despite my bad behavior. And that he never stopped wanting to be with me.
Talk about impact.
And that's how it sounds like you feel about your W.
