Hope the surgery went well. Relax and give your body time to heal. You may feel OK but you do need to realize your body has to get back to 100%.
Let me tell you about a member of my family. My cousin (I'll call her K) has been married for 30 years to a really great guy. That have 3 kids and seem to get along great. She went through a bad cancer scare several years ago and nearly died but her H stayed by her side and was very supportive. She is now cancer free. About 3 years ago a young girl got in touch with her H. Seems that 14 years before H had had an affair. The affair apparently lasted for YEARS and my cousin never knew. He stopped the affair without my cousin ever finding out. Well, what he didn't know was his OW was "with child" when they broke up and never told him. This girl has had a very hard life as her mother is unstable and sought out the father she never knew.
As you can imagine, my cousin was shocked. Not only did she find out about her H's affair but that he had fathered a child while married to her. Not only that it had gone on for years and she knew this woman. She had a choice. Did she want to stay and forgive? What about the girl? My cousin decided that it wasn't the girls fault that she was born because of her mothers having an affair with a M man. She is a troubled but nice kid. K decided to accept her as part of the family. This girl now has brothers and a sister she never knew. She has the stable influence of a whole family and has an escape from the craziness of her mothers life (she apparently has a history of "dating" married men, isn't very interested in her D, etc.). She also has a good relationship with the father she never knew which would have been hard if his wife wouldn't accept her. For the last few years she has been included in family functions, treated like any other family member by my family and is doing so much better because of it.
If it does turn out that this child is your H's and you do end up back together, this may become a choice you have to make. I know this is something that you won't be needing to deal with until much later, if ever (I still have my doubts about the kid being his) but it is something to keep in mind.
My cousin had a different sitch than you for sure. The affair was long ago and over for many years. Her H never left her for this woman. But the fact is your kids will be somewhat related to this child if it turns out it is your H's child. How you view him/her will be important. Like I said just something to keep in mind.