Therapy definitely – because when you found out he was a liar and a cheat something in you refused to let go. Why? When he said “It has to be a secret. My marriage is my priority right now.” That should have made your blood run cold. In the same breath he both said that he’s fine cheating on his wife and that his marriage is a priority.
You fell in love with the person he was pretending to be. Not the real him. You deserve someone who never stops showing you that. Who adores you every day, not just when his wife isn’t looking.