Karley's reply was spot on in so many ways. I'd just like to emphasise how important the needs and wants of the submissive are in a D/s relationship - I see them as so much more important than the Dom's needs and wants. Obviously both are still important and it's necessary to discuss these constantly, but at the end of the day if the sub isn't OK with doing something (on the one occasion or indefinitely) then it's the sub who "wins" and gets their way, the Dom cannot force anything on you that you do not want.

Hope these replies have helped, and as for "wasting" anyone's time so long as you're honest and upfront about what you're feeling (and your uncertainties) then you won't be wasting anyone's time. Besides which, nobody should instantly expect something from another anyway, expectations come over time :-)