The way i see it:

You are no more a slut just because some guy online labels you one than he is a master just because he labels himself one.

i am so so sick of being approached by self proclaimed doms demanding my respect without giving me any - without even bothering to look at my profile which clearly states i am taken.

And i agree with what most of you have said above - i am HIS slut, it is a term of affection and acknowledges that i am always available to him. i am also completely faithful to him, so not a slut in the traditional sense.