HA,
FWIW, I've heard several men share in AA meetings their shame at having been unfaithful to their partners. They don't minimize the harm that it caused to their partner. Some of the marriages healed and some did not. In all of the cases they owned up to their responsibility for what happened.
I think summerpeach is right. Give it some time. Part of recovery has to do with facing what he has done and making amends for it. But other work comes first. IF he is sincere about his recovery and IF he is sincere in his remorse, you will find out. And if he's not, you will find that out, too.
Either way, only you can decide whether you can live with what happened. Ultimately, you will wind up having to forgive him (whether you stay or not) for your own peace of mind. It's something we do for ourselves, to let go of the hurt, not something we do "for" them because they "deserve" it.
Hugs, hope the acute pain starts to diminish for you soon.