Welcome to the STD forum.
Most likely you acquired no STD at all. The only STDs that could cause the symptoms you describe are gonorrhea, chlamydia, and nonchlamydial nongonococcal urethritis (NGU) -- and with rare exceptinos, all of those would have responded to azithromycin and/or doxycycline. The only slight possibility is gonorrhea, which could be resistant to both antibiotics -- but in the absense of an obvious discharge of pus from the penis, gonorrhea is unlikely.
My main advice is retrospective: you should not have treated yourself without professional evaluation. But what's done is done. At this point, as long as the symptoms aren't too severe, and if you do not develop the aforementioned discharge from the penis, just sit tight and follow through with your plan to visit a GUM clinic when you return home.
Regards-- HHH, MD
With research, I believe the symptoms I'm displaying point towards me having an ngu.
Is this like other stds that can be passed on through sexual intercourse? what treatments are available and how long does it take to clear up?
Thanks