Is it normal that i like to pretend to rape my girlfriend?

Well my girlfriend and I have been together for awhile now and when we do sexual things, I've gotten into pretending to "rape" her, with her approval of course. Also, at the same time, I also feel like I'm doing something horrible despite how much I enjoy it, even though I know it's all pretend. We've done this a few times not, but I'm unsure whether I need help or this is just a normal thing like other fetishes.