LH,
It seems like you have had many opportunities to make this right over the years. Your wife stuck with you for 3 YEARS while you carried on with another woman. But, the real problem is that you lied to her for those three years. How can you change her attitude and make her believe in you? You must become transparent to your wife. Show her the remorse you are expressing here. Pick up the book "Not Just Friends" by Shirley Glass. It is excellent and tell the story of the affair from both sides.