I personally didn't go thru this but I had a friend who went thru something similar. The situation was so distressing that she almost had a miscarraige & then ended up having her daughter prematurely. Thankfully, the baby was fine & is now a beautiful, sweet, healthy child. The marraige, however, never fully recovered & after 5 years of trying 2 "get over" the hurt, the marraige ended brutally as my friend discovered how long the affair truly continued (years!).
My advice 2 u would be the same as to her. If he is really sorry & really serious about fulfilling his duties as a husband to u then he will agree 2 marraige counseling. In the meantime, u might want 2 consider living in seperate residences & allowing him time 2 work out his true feelings alone as u focus ur attention where it needs to be: on ur child. Eventhough u may not b able 2 divorce him right away, u can get a legal seperation. The longer u stay in the situation, the more u will have 2 lose in the long run.