Sammy, I think you would get a lot out of reading the book Corri recommended, "Peace Between the Sheets." It describes PRECISELY the situation you are in (and that many people in this board are in)-- the cessation of sex after marriage, the lack of desire, the differences in desire. Unfortunately the thread discussing this book has focused on one particular aspect of the book which is that the method recommended involves sex without orgasm. For some reason that's ALL people seem to have gotten from the articles Corri and I have posted. But this book is about rebuilding the emotional connection between two people with caring and giving and no pressure to perform or be any way except the way you are right now. If we could get past the "What? No O?!?" reaction, there is a lot of wisdom in this approach.
She suggests simple non-threatening exercises... nothing weird or hanging from the chandeliers, and neither of you has to have ANY desire to do them... you just have to be willing to be close. Chances are, desire will kindle by itself, but the emotional connection is always the top priority.
The book addresses why your situation is sooooo common and why it is neither person's fault and it is not the fault of the relationship. She makes a good case for why it is biologically based.
This book will make you and her feel totally normal in your desire levels, whatever they are. In fact, if you get it, I predict she will eat it up with a spoon-- I did.
This is a huge breakthrough. So if you are going to stick out this relationship, be prepared for a lot of work. Even if you can identify and fix the lack of desire problem in her, there are tons of other issues at play, and half of them have to do with you.
So check into any physical problems, then do some serious study as Lil suggests with her book. I would also put Shnarch high on your list as well as some books on codependency (for you) and start to look into both of your FOO issues. I think you both seriously need to get into counseling too. The good news is that you two may be able to work through these things faster than others here who have been stuck for years and built up lots of resentment.
Do not even THINK about marriage until you two what worked through a lot of this stuff. Otherwise you will both harm the innocent children to come.
But this book is about rebuilding the emotional connection between two people with caring and giving and no pressure to perform or be any way except the way you are right now. If we could get past the "What? No O?!?" reaction, there is a lot of wisdom in this approach.