LL, I agree with 1210 that you need help from a professional on this.
I would also say to you that you have your own boundaries that you have to establish with her that she cannot cross. This is probably one of them Luke, she cannot expect more out of you than you can give. I have to tell you that in my gut I would say she may be testing you to see how much you will tolerate. I can't imagine anyone beleiving that this is a good idea and believing that their spouse would accept the idea.
Anyway Luke, I dont have a lot of time this am, just checking in with you and when I saw this.... had to say something. Remember we established that only you can determine what being a man is, well also only you can determine how much that man is willing to take befoore he says no more.