Well it's not something I go out of my way to talk about, but I'll share here in the hopes that it will help. I told my t about my bdsm relationship as soon as I had established enough trust with her that I knew she would be able to handle it. (It sorta came up in a dream, and we do a lot of dream work, so that was the perfect opportunity to get it out there.) I also told her that it wasn't something I was looking for help with, as it is a part of who I am that I don't want to change. And she was fine with that. It wouldn't sound rude for you to ask, and like miguel'smom said a good therapist wouldn't be bothered by it anyway. I wish you luck!