The Sidney Borum Jr Health Center on Boylston St specializes in providing services for GLBTQ and other "at risk" people (up to age 29). I'm not sure of their record on kink, though. I assume it very much varies by the actual counselor. I have used their mental health services in the past and had a generally good experience. Well, actually, I spoke to two people there, one of whom was fabulous and who over the course of six months or so really helped me turn my shit around, and then when he left I saw someone else who was not nearly as good. So YMMV, but in general the Borum is a very cool place, perhaps worth looking into.