This almost sounds like you could forgive him if he'd have went to a pro, the idea that you could be embarrassed by his actions makes it intolerable?
It's about respect and honesty. Marriage is between two people who are supposed to love and honor each other. There is no honor in treating your spouse like a throwaway and opening the marriage up to outside influences. It's not the physical infidelity that kills you - dogs ####, hamsters ####, they rut like the animals they are and who cares? It's the thought of someone else being emotionally intimate with your spouse that destroys you.