Kara

I'm familiar with your sitch. When you say NC, is it really NC? This OM lives very close to you, how are you going to keep from seeing him?

Also, what are you doing to protect your weaknesses so that this does not happen again? Is there an addiction involved? Why did you give yourself permission to do this?
You need to know so that you can prevent it from happening again.

Have you two filled out the EN questionnaire. If not, do it. Learn his ENs and start meeting them the best you can. Be open and honest about your A. Don't hold back to protect him. He needs to know ALL the answers to the questions he asks. If you hold on to the truth it'll eventually come back again and he will be devastated over the lies the next time. It'll make it that much harder to begin to trust you again. Get it all out NOW. I can't stress that enough.

Work on you. Be a better person. Be a person that any man would want for their spouse. Show him that you can change and that the changes can be permanent. Protect him. Protect your child's family.

This takes alot of time. It's not a sprint, but a long marathon. Tell him you will do whatever it takes to help him recover and to recover your R. And mean it.

Say you're sorry. Say it more than once. Say it instead of trying to defend your A (don't know that you have). It helps.