Hi,
I am really new to this forum and I myself am not into bdsm but I have close friends who are. And what you write here about the man you are with has nothing to do with bdsm but everything with sadism.
Maybe he once was into bdsm and got his guidelines mixed, but you should not suffer for that. There are safewords for a reason. You are supposed to know that you are only going to be pushed as far as you can take, and not an inch more. And I am sorry to say this, but if he loved you, he wouldn't torture you. It is mental and physical abuse and I so wish, I could punch that person a good one. (Okay so violence is no answer, but wishing and not doing, so...)
I can only imagine how this betrayal hurts and I know the fear of being alone and unloved, but... this is not love. Cheating is not something I normally condone, but take this experience as an example of what you should have. As something you can have. It'll be hard, because you have to find the strength to leave the man who is hurting and terrifying you, but it'll be worth it.
it sounds like you had made good progress, don't let him destroy that for you. I wish you lots of courage.
<Edited by CB - capital letters and paragraph breaks>