Oh my god!
GM, I'm so, so sorry. Even if all the things he said about you were true, which would shock me since you don't come off that way in the slightest, it still would not excuse him lying to you and sneaking around like that. What a complete lack of integrity. How dare he call you a bad sub... a dom (not to mention a good human being and partner!) is supposed to have a little backbone, and if its true that he wanted to leave you all this time but didn't speak up, then he's a coward, plain and simple. Nothing excuses carrying on a deception about something so personal, not to mention for so long.
You deserve so much better. Again, I'm sorry.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.