I have fallen out of love with my cancer stricken wife, how best do I tell her? and my friends and family?

I have been with my wife 8 years (6 dating, 2 married). Before we got married I had my doubts and almost didn't get married, but all my family and friends loved her and would continually tell me how great a person she is and that we make such a great couple. I went ahead and married her thinking that maybe I was being too picky or commitment phobic. The 1st year of our marriage was frustrating and difficult for me, there were many times I felt that I didn't love her or that we were incompatible. But we lived in a tiny apartment and that can be frustrating for anyone. So I hung in there and we bought a house a year ago, still I have feelings of incompatibility. She is completely oblivious, I've tried to point out some of our incompatibilities but she just seems to laugh it off as 'every relationship has it's problems'. I never broached it with my family and friends because they all absolutely love her. I am so unhappy now, perhaps counseling would help but I doubt it. I don't even want to try anymore. I'm beginning to feel that I married her just to make my friends and family happy and not me. I'm not sure if I ever truly loved her. She's a good person, but I'm just not in love with her. To make matters worse, about 6 months I was about to ask for some time apart when she was diagnosed with cancer. I stood by her and she has just about beat it. I thought the experience might have changed her, but it doesn't appear to have. Now I want out of this relationship, what do I do or say?