affair resulting to a child

Maybe you could help me understand the process of ending the affair wherein the unfaithful spouse has a child with the AP. No contact rule is not applicable. Or can it be possible? I have opened myself to the idea that he would have visits to the child. Are there any 'rules' or steps that I need to know? D-day was 5 months ago and I still feel so much pain. The unfaithful spouse is not helping as he appears to be not driven enough to take the necessary steps to make drastic changes. We have 2 lovely children and I am barely keeping it together. Help!