It was a combination of loving to be Dominant/in control and also being asked to let that side of me out. Except I think it turned out that I enjoyed that side more than my partner thought I would, or something like that. "Buck" wasn't completely new to this, but I think in hindsight that it was one of those things, like you said Ozme, where the fantasy would have been better left as a fantasy.
And yes, I'm a poly-switch. I'm submissive in 2 relationships and Dominant in 2.... well 1 now.These are my first BDSM-flavoured relationships. Exploring my subbie side is fun, and new, and surprisingly just as instinctive as wanting to control and 'play' a submissive like an instrument (course I still care about them and want them to enjoy, but something about seeing them squirm, even if it's just imagining it online... yummy.)
Buck came to see me in between my posting that and posting this. We had always planned to move our relationship from online to R/L. I wasn't perfect the whole time, by a long shot, because I wasn't sure what he wanted from me and so was concerned with taking more control from him than was My right (cause of being in the 'limbo' of not knowing what we were at the time.) Also in between that time i went to live with one of my Doms (Sir being only online, Master being r/l). These changes made it clear that it's just not a good time for me to be trying to be the center of someone's world the way Buck wants, because I have my hands full taking care of myself. So I don't feel quite as much like a failure for it anymore-- I realize that's alot to ask of anyone, especially someone who isn't entirely sure what's going on.

I don't think anyone would think badly of someone who can't really handle trying to be a 24/7 half-online half-R/L Domme for someone who doesn't want to be a sub but is just needing attention and threatening suicide... Someone who needs a therapist, not a young Domme.

which raises the other question of, now what? the relationship isn't completely over (the D/s part definitely is on hold for a while, if not permanently squelched, tho) but I still feel responsible for him, especially as I'm worried he'll actually kill himself without me. Is it alright for the Dominant or ex-Dominant to be the one to end it, or do we have a responsibility towards those who rely on us to be there for them until they walk away? I'm trying to follow some of Sol's advice, as well as that from my Doms (which is really more of the same) but things continue to seem to be getting worse instead of better. If it had been vanilla through and through, I'd just ditch the guy and move on at this point. At what point though do you stop trying to work things out and just start breaking it down? is it different in a D/s relationship than a thouroughly vanilla one?

many thanks for all of You who have responded and been so helpful