Sexuality is part of (nearly) everyone's life and I can guarantee if your T has been in the job for any length of time she'd have heard it all before. It's natural to feel scared as it's such a sensitive and often painful topic and I think LT is right on point by suggesting you discuss your fears with your T first and hopefully feel more reassured that it won't change how she sees you.
It took me a long time to talk about it with my T but in my case it was due to strong feelings for her and was terrified that she'd think I was viewing her in that light (which, to be honest, I kind of was at times). It helped me to write stuff down and share it that way first. Even now I can't go into much detail but I'm getting more comfortable with it. It's definitely a process.