I want to thank everyone for their interest and opinions. Just a few comments I need to make. First, I have a four year old daughter and my fiancee intends to adopt her--he is her father in every way but blood. My ex has no contact and provides no support (financial or otherwise). So, in regards to the kids factor, that is already a factor. I don't want to take my daughter away from the only father she has ever known. They are extremely attached and he is a great parent.
Second, no erectile dysfunction, just low desire. Physically, everything works fine. If I stimulate him, he will become aroused. However, it's no fun always being the initiator and wondering if he is wishing I would leave him alone.
Third, I have found no evidence that he is gay. Lastly, he has denied any past sexual abuse. Overall, I'm at a loss to explain this. Everything is great in our relationship, we get along well and have no money problems. His work can be stressful but I don't think that's it.
Hopefully since he is willing to deal with the problem things will change. Again, thanks for the interest.