The first time for me as the BS, I was just there for the kids, for the family, I didn't want another woman raising my kids. We had another child, moved, made another life. He would never tell me what really happened, never remorseful.
Fast forward 15 years, he had another "relationship" that I found. Who knows how many more as he traveled. If they don't own their stuff, and they don't figure it out, religion or not, cheaters cheat and liars lie because they are selfish and it's about filling a hole in their soul!
Sorry for your pain, it took me years to get over the first possible affair with our daughter's birthday being the day he asked for divorce the first time around.
As far as not talking about it, lived that too! His way of not having to deal with the fallout and consequences of doing something he shouldn't have.