I had mystery testicular pain for years. It was crippling and no doctor could figure it out. I saw literally dozens of doctors, had several MRIs and CT scans, and nothing turned up. Then I went to university and learned all about human anatomy and thus I learned most urologists are surprisingly ignorant of the topic. Certainly every one I saw was.
It was two issues: I have a connective tissue disorder which led me to strain my cremaster muscle through daily activities, and I had compression of the genitofemoral nerve due to tight iliopsoas from working a desk job. I’ve included my protocol if you want to give it a try. It cured me and has helped a few gents I’ve corresponded with online. I’ve been mostly pain free for over a decade now, with it only recurring when I get lazy and don’t adhere to my system.
Cremaster strain: wear an athletic supporter with a plastic cup whenever possible. It needs to be tight enough to immobilize your testicles. After the pain starts to abate, stop wearing it in bed for a week or two, then for gentle walks, increasing in duration as tolerated. Eventually cease wearing it altogether, but still keep it for recurrences.
Bonus balls exercise: the cremaster muscle is originally a part of the obliques. For some (but not all) men, bicycle crunches with a hard “crunch” of the obliques at the end will result in contraction of the same side’s cremaster muscle. You’ll know if this is the case as your testicle will rise, as if by magic. Obviously do this exercise after the pain has started to resolve. This is also one way to see if the muscle is your issue: it may hurt when or after it contracts, but this isn’t always true
Genitofemoral nerve compression: firmly (but not too firmly) stretch your iliopsoas twice a day for 30s each. No more, no less. The “blaster pose” in this video is what I do.
Additionally, strengthen the same muscles doing the exercises found in this video.
That’s it! I hope this helps. Feel free to ask questions, I’m an open book.
Good luck! I always wondered if driving was a factor as it was only on my right side and driving requires a surprising amount of iliopsoas activity.