Welcome back. But I'm afraid I can't help much -- at least not with answers you will like.
In the absence of symptoms such as abnormal urethral discharge, it is unlikely you have NGU (NSU) or any urethral STD, certainly none that requires treatment. Nonchlamydial NGU is probably harmless for patients and their partners alike, and there is no reliable test for it.
In particular, there is no PCR test for NGU. The test that comes closest to evaluation for asymptomatic urethritis is very low tech examination of a urethral swab for elevated white blood cells. It is unreliable, with high rates of both false positive and false negative results. Even if increased WBC were found, treatment would not normally be reommended in the absence of a positive test for gonorrhea or chlamydia, or evidence of abnormal urethral discharge -- either by symptoms or observed on examination. Therefore, in the absence of symptoms most STD experts do not recommend it for asymptomatic men. We used to do it in my STD clinic but stopped several years ago, because of high rates of uninterpretable results that made little or no difference in treatment decisions. Further, the utility of such an exam or treatment undoubtedly is even lower in men who have recently taken azithromycin. (Why did you do that, by the way? If you're in the habit of routinely treating yourself for presumptive STDs, I recommend you stop.) I cannot speak for usual care in the UK, but I'm pretty sure most UK GUM specialists would agree with all this.
For all those reasons it sounds like you have had state of the art care for asymptomatic heterosexual men seeking screening tests for common STDs. Nothing more need be done. I do not recommend treatment with doxycycline, metronidazole, or anything else.
None of the tests mentioned here would be affected by acyclovir, marijuana, etc.
Since this is your second question on the forum in 2 months, I'll point out that MedHelp permits no more than 2 questions every 6 months in each of the professionally moderated forums (see Terms and Conditions). No more before mid-March; I don't want you to risk losing your posting fee.
Regards-- HHH, MD
Thank you for your reply. It was really helpful.
I had sex a couple of months ago and the condom broke. About a week later I had stinging/burning after urinating and ejaculating. This is why I became concerned and took the zithromax but it hasn't helped with my symptoms. I took the zithromax a few weeks before I had the PCR test. Could this have adversely affected the test results?
Like many of the people on these forums I know I'm being overly anxious and that it will feel better in time. I'm sorry for asking another question.
Once again thanks for everything and for letting me know about the posting fee. That'll be it from me now.
Take care and have a good day,