Alexi is right . . . the first step is talking to her. I would try to avoid pinning the whole problem on her as that might make her defensive - I would instead approach it from the angle that you want to make your sex life better and more satisfying for both of you.
And again as Alexi said - try a "romantic weekend" somewhere new and different. Introduce some new elements that might help her feel sexy - Honey Dust, Bath Oils, Lotions, whatever it takes.
Give her the benfit of the doubt - she's not a mind reader, she may have desires that she hasn't told you about but the doors to this kind of communication may not be opened yet. Make sure they are before you close the door on your marriage.
I think the mistake a lot of us make is thinking the state-appointed shrink is our friend. - Jack Handy