I can understand your feelings and have been where you are 5 years ago. A close friend who knew nothing about what was going on told me the following:
sometimes when we are at our low points there will be someone who seems to lift us up. We feel so good when we are with this person that our feelings become misguided and we begin to see that friend in a different light. They are filling a hole inside us that our partners arent able to fill at that time. While we are having contact with that person we cant really see things for what they are. The feelings we think we have for this other person seem so much more real and we being to doubt our feelings and purpose with the other person.
I cut off all contact with this person. I found that it was easier to think through things. I decided that I would give my relationship another shot without outside influences. I can say that I am glad that I did hit that point in my life. I value what I have and now realize that those feelings were not real, I was confused and that person was able to fill a void that my parnter could not. I am thankful that I never followed through at that time.
I hope that it all works out for you. From what you have said you have a supportive wife who loves you. It takes work to keep a marriage going and we all change. Maybe just the two of you going out to dinner, having a date again. You never know you just might find what made you fall in love with her in the first place.
Good luck.