I think ONLY a self-centered narcissist could act as you describe. There was no reason to be so unkind was there?! Most of us, if we wanted out after that many years (and I did at some points!) would find a way to take the blame for things, not direct it to the person we were leaving. Or, at least sit down with the MOTHER OF YOUR CHILDREN and try to explain why all of this was happening. He wasn't unhappy for all those years, more likely he started having some stupid mid-life crisis and decided to step out on you and try to recoup his youth. I seriously doubt there was no other woman. He is not in a relationship now?