role reversal

My girlfriend and I often practice the Dominance and submission in BDSM. We're still fairly new to it (we've been doing it for about 8 months or so). As far as anyone's concerned, we seem to have the basics down; before we start I ask her what she wants to do or try. Handcuffs, blindfolds, choking, and slapping are involved most of the time. I'll tell her to do things, and she'll listen. Sometimes she'll disobey me and I'll punish her, though I'm starting to think she disobeys JUST to get punished. Punishments usually include teasing, slapping, or even a good ol' fashion spanking, which always gets plenty of aftercare.

Now, while she always loves being submissive to me, and as much as I love dominating her, sometimes I get in this mood to switch, to have her dominate me. At first it was small things like scratching or choking. But lately I've been craving for her to do more. I honestly can't say for sure as to why I want this. Am I really a sub posing as a Dom? Do I want to know what it's like to feel controlled sexually? Maybe I want to see what it's like for her? Or maybe I want to see if she can really take control?

It's gotten to the point where about a month ago I learned about anal play, for myself. And now, I've just been dying for her to take me from behind.