First off... I would like to say how PROUD you should be of yourself for seeing this issue as a problem in your marriage since it is hurting your wife and for taking steps to end it.

I would suggest that you do some reading on porn addiction (much can be found on the internet) - try looking into books written by Dr. Douglas Weiss, awesome author in the subject of porn/sex addictions.

List of his books:
http://www.drdougweiss.com/Resource.html