I do know that the affair being a secret adds to the excitement of it. The brain chemicals of being 'in love' makes even the smartest of people act like idiots.
You may want to post on the Infidelity board. They can give you advice on how to go about confronting him if you decide that's what you want to do.
I'm sorry I can't be of more help in this area. I didn't have to contend with this problem as my H told me about the ow when he dropped the bomb and moved in with her the next day.
You sound like you have a very good head on your shoulders and are very strong. That will serve you well in this.
