How to save our marriage?

My wife told me she wants a divorce. I was saddened and begged he to reconsider. It's been rocky in a marriage lately she discovered i was having an affair and was crushed. I told her it was a mistake and my mistress meant nothing to me. We agreed to go to marriage counseling to resolve things. However she told me she can't do it anymore after she found me in bed with my mistress again. I told her i was sorry but i we haven't had sex in 2 years and i have certain needs. I do love her but i don't know why she won't have sex with me. This started before my affair. I don't want a divorce but that counseling doesn't seem to be helping. My mistress is falling in love with me also and i don't want that at all, How can we salvage our marriage?