I agree with both NGG and Claire. For me, BDSM always incorporates sex. Whether Master and I engage in floggings or intercourse, it all is about sex. And while growing up I also hated to be spanked and I think it wasn't so much physical pain that I didn't like, but the realization that I had failed somehow. I had failed to be a good girl, I had failed to get my parents' approval, I had failed to obey them, etc. Now that I am an adult I love spankings from my Master. And for me receiving pain from Him is sexual. As NGG said, masochism is sexual.
While growing up I also had fantasies of being locked up and held against my will, and I still do today. The fantasy of being kidnapped, raped, forced to submit to a stranger, is a well-loved fantasy of mine.
BDSM is what connects me to my Master, on a very deep emotional level. I could not live without the BDSM in O/our relationship. I learned in my first (vanilla) marriage that there has to be more to a relationship than just sex to hold it together. BDSM helps Master and I to connect on so many levels. Would W/we still love each other like this if W/we were not a BDSM couple? Now that, I can't answer for certainty. But I wouldn't want to test that theory. I can't go back to vanilla and if something (Goddess forbid!) were to happen to Master and W/we were no longer a couple, I would seek out another Dom to be with. Sex is easy to obtain. It's something I could do with nameless strangers in the dark. But I wouldn't be happy or fulfilled doing that. I have to have the BDSM as well. Without it, sex is dull and life is dull as well.