As heartbreaking as this is harvest_moon, you have to realise that this is not your doing. He made the decision to cheat on you not once but twice, from what he says. He chose and he, and he alone, decided to act on this attraction. If you truly love someone you won’t contemplate looking at someone else, let alone sleep with them.

It will take time to get back on your feet and understandably your trust has taken a nose-dive, but you can get back up again. With time. Let yourself heal & give yourself permission to move on without him. You will be better off anyway as his way of relating to others (to you for instance) is not healthy and he would have dragged you down sooner or later.

For now, you need to take care of yourself and think only of yourself i.e. your emotional and physical well-being.