First things first. I think you need to decide which route you want to take: do you want to wait the affair out and hope to attract your partner back by being the better woman OR do you want to actively work to bust the affair and show him tough love?
Right now it sounds to me as if you're not sure. These paths involve different tactics so I'm not going to advocate anything until I hear which way you want to go.
If you love somebody, set them free. http://tinyurl.com/2empx2g