I must say I have been rather fortunate ln this respect.
A long time ago, in my twenty's, back in the seventies, I had a long time relation, with a smart and attractive language student who was very much into medfet. Maria was also a bitt bossy and she had decided that we would have sex only on her terms. Every time we were to have sex, she imposed on me a complete medical exam, me stark naked as she kept her clothes on, which allways ended with my rectal temperature being taken on her lap and included a lot of stething.
As I was very afried of doctors, Maria had assured me she knew nothing about cardiology and could not tell if I were dying. She had stolen her stethoscope from her sister who was a real MD.
When she stethed my heart, she would often lett me listen to my heqrtbeat, and sometimes her, And the noises I discovered were fascinating. Besides, as one of her hands moved the disc of the stethoscope on my chest, her other hand would casually play with my erect nipples. A very sensual experience.
We also used her stethoscope, and a second one we bought, to monitor our heartbeats when we were having sex.That was also extraordinary and added a lot to our sexlife.