Preggo, This isn't about forgiveness, it's about moving on and creating a better marriage. I've never considered forgiving my wife, I just try to have a great relationship with her without looking in the past. I would suggest you BOTH do the same. It takes two to make a bad marriage. Was it right for him to stray? No! But there were reasons why he did, and that's what you should focus on fixing.
What your husband really means by forgiving him, by the way, is that he doesn't want to live the rest of his life with you bringing up his A, making him feel guilty, and hitting him over the head with it every time you have a disagreement. My wife felt the same way as your husband- afraid that I would never let her forget her affair. I knew that if I allowed myself to use her affair against her in ANY way that she would fall back out of love with me. You just can't deeply bond with someone that uses the past to bludgeon you.
I know that what I just wrote may seem like an impossibility to you, but I suggest that you come to peace with the fact that you must get there. If your goal isn't to create the best marriage ever known to man (we all fall short, but it's the goal :-)) then you are setting yourself up for failure.
Also, I see you are posting all over the place. The way to get the best responses is to stick with one post string in one forum. I would suggest the "Newcomers" forum to get the most traffic.