Try to be optimistic. You've got to talk to your wife honestly and tell her how important it is for you to have sex, and also that it be loving sex, not duty. Tell her the consequences, that you will not be able to remain in the marriage without it.
I agree with Alisaun, there's something going on here. Past life trauma playing out as laziness, disinterest or some such. That the two of you are so well "paired" otherwise indicates that the two of you are strongly linked karmically. I would try to explore this. If I were you I'd contact Andreas Moritz (he has an "Ask Andreas Moritz ") forum here on the site, or his web site at ener-chi.com. He does telephone sessions of "Sacred Santemony" that would probably benefit your wife a great deal (BUT she has to be interested in working it out).