Not everyone is a switch and most switches can't turn from Dom to sub like one flicks a light switch. Changing mindsets can be very difficult and having to be provoked into Dominating is not a good thing. A good Dominant doesn't scene when they are impaired by strong emotions or drugs or alcohol. It is too easy to go too far.

Try and plan on times when you will be the Dominant partner--scheduling might give you a chance to come to the right mindset without getting angry first. Also, negotiate a scene (what does he want to experience--humiliation, cock torture, denial, etc) and write up a script beforehand. That might make it less real to you but it might be easier than trying to do something that is not organic to you.

Good luck to you both.