My fiance went from Sub to Dom last night,my mind is completely blown! [FM]

I have been hinting at my fiance about my interest in trying BDSM for some time now. We both could definitely be considered Subs so our sex so far has been alot more about just giving and trying to satisfy the other as much as possible. To this time he hasn’t been comfortable with being rough with me. When I’ve directly asked for even some light choking he’d try but obviously was far from his comfort zone. And I understood, he’s pretty significantly bigger than me(I’m 5’1 he’s 6’2) and stronger. That was fine because our sex life has been amazing regardless so I wasn’t upset and we otherwise share interest in alot of the same fetishes. But last night something switched.