Welcome to the forum. Thanks for your question. It's a pretty frequent one -- men with testicular discomfort and worried about epididymitis. I'm going to take this opportunity for a blog-like response that will be helpful in responding to future questions as well as your concerns.
The evidence is strong against epididymitis as the cause of your symptoms. First, the only unprotected exposure(s) you have had apparently were oral. The only STD acquired by oral sex known to cause epididymitis is gonorrhea -- and that would have caused an overt discharge of pus from your penis for at least a few days before causing epididymitis.
Second, epididymitis rarely causes the mild sort of symptoms you describe. The main findings of most sexually acquired epididymitis are severe pain, obious enlargement of the testicle, which feels abnormally hard and is very tender to touch. (In the STD clinic, sometimes epididymitis is suspected just from the way the guy is walking, because of testicular pain.) And as implied above, most men have abnormal urethral discharge as well -- even if not the overt pus seen in gonorrhea.
Third, sexually acquired epididymitis almost always involves only one testicle, never both. As for one testicle being lower, that's the case in every adult male. I'm sure you're just noticing something that hasn't changed.
Fourth, there is an obvious alternative explanation for such symptoms: exactly as you suggest yourself, they are typical for genitally focused anxiety, which is common in men following sexual exposures that they regret or cause anxiety. The mechanism of pain is basically teh same as tension headache: increased tension in pelvic muscles instead of the head. And whenever someone suggests his or her own symptoms have an emotional or psychological origin, usually s/he is exactly right.
For those reasons, I'm confident a professional examination would find nothing abnormal. But at the same time, that normal evaluation, along with negative STD testing, might be more reassuring than anything I can say. So I'll have to leave that decision to you. However, I'm pretty certain no harm will come if you don't do it, or if you sit tight for a week and see what becomes of the symptoms. If you gain confidence (emotionallya s well as intellectually) that it's nothing serious, the symptoms probably will melt away.
I hope this has helped. Best wishes-- HHH, MD
yup....relax man. im just getting over epidi-feels like i got kicked in the nuts-itis. mine started with shooting pain. we're not talking a twinge, we're talking a lightening bolt of pain from your testicle to your prostate thru the vans def and up thru your bladder. enough to knock you off your seat. then you pull down your pants and look down and your sac is red, hurts to touch, hot, and one of your testicles hangs at your knees. then you know you got epididymitis.
Thank you for your very detailed response! Incidentally, I'd like to thank you for the work you do here in general - this is one of the few sources of information about STDs I've found on the internet which tends to decrease, rather than increase, my anxiety...