On my way out, just want you to know you are heard.
Sounds like he is blaming YOU for him cheating, nope, it is all on him.
BTW, the PT can be fired because it could be a violation of professional ethics.....
Understand cheaters lie and minimize, it may be likely that they had sex, just putting it out there..
I hope he has stopped physical therapy with this woman. He can never have contact with her again, no phone calls, texts, social media, please stay vigilant and ask him for access to everything...including emails and phone.
Honestly, if it were me, I would contact her employer.
In the meantime, find a good therapist for yourself to help walk you through this nightmare. Meet with your MD for temporary medications if you are having difficulty coping or sleeping.
Also, you are correct, if he was so miserable, he could have communicated his feelings to you...instead he chose to cheat.
Marriage counseling should be put on hold for now, both of you need individual counselors, the marriage didn't cheat, he did.
Also, seek support of TRUSTED family/friends/clergy if you are so inclined.
He should be making every attempt to help you heal, a good start is a book called How to Help Your Spouse Heal From an Affair.