I'm late to this thread but I'll echo all of the others and I'm glad you've walked away from this train wreck waiting to happen.
Not because you are still M or because of how long you've been S but because this sounds all around toxic.
I'm considered a madhatter here - it is not something that I accept myself.
Identifying as a WS isn't at all comfortable but that isn't the reason why. It is because it makes the sad clown a BS and for some reason that makes me livid. I did not betray him.
I sure did betray myself though. Not for issues of sexual morality because I don't personally see an issue with sleeping around when you are not in an exclusive relationship but because I was broken, sick and bleeding and so full of rage that it harmed me. I didn't even do it to hurt him. I was hurting me.
Sometimes when you feel powerless or like you've lost control (not of faculties but of.... pride? illusion? Something in that area) hurting yourself can feel 'good'. I felt more in control when I started hurting myself more than he had hurt me.
False control of course - I was anything but in control.