I have never heard about anything like that in a "stand-alone" person, but there have been Christian sects in the past that have made group sexual mutilation part of the initiation protocol, and yes, the descriptions are graphic and horrifying. A friend of mine studied them in her PhD program. They were quite large scale at some point, so, in the historical perspective, you are not alone (I do not know whether the sect members received pleasure from self-harm; quite possible that they did).

You need a professional you can talk to freely - try a sex therapist, AASECT - Member Directory.

Also, you should treat the T as a service provider. You should not feel ashamed. You have no duty to the T other than to pay the agreed upon amount. The T is your car mechanic and you happen to have a really rare, unusual, one of a kind car with a rare, unusual problem. Nothing to be ashamed about, but the T needs to have experience treating your rare problem.

Good luck.