You know, the weird thing about "forgiving and forgetting" is that it doesn't ever actually work out that way. We can forgive someone, but how often do we really forget that we've been hurt before? I'm not sure we should forget, either - otherwise, how would we learn or grow?
I found some links about remaining together after infidelity that I hope might be helpful for you:
Staying Together After Infidelity
USATODAY.com - Staying with one who strays
Dr. Phil.com - Advice - Moving Forward after Infidelity
I hope those are a little helpful.