Hey Cheetah,
The "calculi" means a kidney stone. If you are starting to pass that, lower pack pain would be a likely symptom, often very intense. Another symptom I have had as well as heard others talk about is some pain in the penis will echo how far the stone is in it's path from the kidney to the penis and out. Not talking about pain as the stone finally reaches the penis, but for example pain near the penis base when the stone is on it's way, and then further toward the penis tip when the stone is almost to the penis, etc.
I'm mentioning this because there seems to be a lot of referred pain with that and I'm not sure that what you're feeling isn't related. I have no knowledge if that can show up directly to the scrotum. But then anxiety can alter symptoms.
I am not the best for STI advice, so I won't comment on that.
Hi your correct as giving her oral sex you would not have symptoms in your lower body but in your mouth area.