Having affairs is an IMMATURE reaction to what life is throwing at you
So he feels less than a man because, infertility? Not liking the stress? - Go out and fuck someone younger.
Implement immediate boundaries and go No Contact. DO NOT make the mistake I made which was to chase him and cry and beg all over him and talk reconciliation (as the counsellor said 'he has just learned he can get away with it').
Be strong OP.
What you should focus on IMO is his COMPLETELY UNACCEPTABLE, ABUSIVE behaviour over Christmas whilst he was twisting his reality in order to justify what he wanted to do.
He demonised you so that he could change his morals in order to do something HE KNEW was bad. He dealt with the stress by running away. What kind of a man does this dishonourable sh*.
You focus on that? Refuse to have anything to do with him right now? NOT talk about the future?
You have a chance.
IF he has the character to face himself and change his behaviour, there is your clue to whether you have a future, because what's done is done. If he doesn't - divorce.
Your pain? I am afraid there is only one way through it, and that is through it. This is classed as PSTD traumatic. There is nothing that will ever hurt me as much as being intimately betrayed, and my life has not been easy. It's devastating.
One day at a time OP.