You don't say whether you were the insertive partner (top) or receptive (bottom)--but since you don't know for sure about condom use, I assume you were the bottom (the top of course would know for sure).
You describe classical symptom not of prostatitis or other genital tract infection, but of acute proctitis (rectal infection). The most common cause of proctitis combined with parethesisas (presumably you are medically trained, using that word?) is herpes. Chlamydia, gonorrhea, campylobacter, and other organisms can cause it; you could even have lymphogranuloma venereum (LGV), a particularly severe form of chlamydial infection that in recent years has reapperated in gay men after 2 decades absence. Syphilis also is possible, but less likely; it usually doesn't cause such severe symptoms. On the other hand, all these possibilities are less likely if a condom indeed was used and remained intact--but you seem unsure.
The dysuria poses a slight uncertainty; not normally a symptom of proctitis. However, rectal spasm/tenesmus can cause referred pain to the genitals, which you might have perceived as dysuria. The apparent lack of urethral discharge also is against a genital tract infection.
All in all, my bet is on herpes proctitis--when tends to be favored by the fairly long time (2+ weeks) it took to resolve, as well as the apparently fairly severe symptoms and the paresthesias. It is a shame you took doxycycline without diagnostic evaluation; that was a very big, very dumb mistake. Doxy would have no effect on herpes, but it screwed any chance of diagnosing any of the other possibilities--so if it isn't herpes, the odds are you'll never know the cause. But I strongly recommend you get the direct care you need (it is commonly said that the physician [or other health professional] wo treats himself has a fool for a doctor). The the work-up include diagnostic tests for HSV, especially HSV-2, and a syphilis blood test. You also should discuss the possibilities with your partner, who should be examined and tested for all the above conditions.
As for HIV, your symptoms certainly don't suggest it. But the highest of all HIV transmission risks is receptive anal intercourse that results in proctitis, especially if it is herpes. Of course you should have asked your partner his HIV status; no gay man should ever have sex with another man, even intended safe sex, without first asking about and mutually discussing each others' HIV status. If you did that and your partner is negative, obviously the risk is zero or close to it (accepting the slight chance he was recently infected). But if his HIV status is unknown, or of course if he turns out to have HIV, you need HIV testing through 3 months after the exposure.
I think that covers all your questions. See a health care provider about all this, be frank about your risks and your concerns, and follow his or her advice.
Good luck-- HHH, MD
I forgot to add.
Another symptom of very tender left inguinal lymphadenopathy
That could go along with herpes--or, less likely, LGV or syphilis.