I am just the same on the other side. I can make vanilla love when it's appropriate, but at some stage I have to think of it as rape or abuse, or it's just cold potatoes. That was what finally broke me up with my ex: even though I accepted her wish to drop BDSM from our love life, she knew me well enough to know it was still going on in my head, and she couldn't accept that.

It's nothing to be ashamed of: we are what we are. You should be proud that you can please your Master by going along with his wish for an occasional vanilla fuck, even though it's not really your thing.