Forgiving a cheater...help

He bought nudes from women. We had discussed that even flirting was cheating. We had a good sex life. I don’t send photos because I’m insecure and have had bad experiences in the past. He still went behind my back and bought nudes from lots of women. How do you forgive someone for that? Can you even? He keeps begging for forgiveness but I think he’s just panicking since we lived together and have two kids.