Don't confront him yet. Take the time to figure out what you want to get out of the conversation. Also, it would be best if you knew beforehand how you want to handle the affair. You have two basic options: wait it out or actively bust it. There are examples here of people who have gone both routes. I recommend you think about it now because the mindset required for each is very different.
I'm so sorry you have this added issue to deal with. Many of us know the pain you are in first hand. Go ahead and vent here when you're ready, you will find support.
If you love somebody, set them free. http://tinyurl.com/2empx2g