So is killing people who piss on you.

I don't care if it was unicorn farts with invisible sprinkles, what you did is sexual assault. Get therapy, stop dating.

Practicing a kink or a fetish on someone else without their explicit, ongoing consent, is sexual assault. You fucked up from the start, by regularly sexually assaulting her.

You need therapy, to learn not to sexually assault people. You need to be absolutely single, not even casual hook ups, until you learn to apply consent even if you don't want to apply consent.

You fucked up because you sexually assaulted her. You lost your girlfriend because you sexually assaulted her.