Hello and welcome to HCM.
Thank you for your query.
A few things I would like to highlight from your query before suggesting a diagnosis:
-You respond to Azos, which is an antibiotic
-Burning after urination or while urinating
-Lower back pain
-Urgency to urinate
-Spotting after urinating
Let me inform you that all these are symptoms of a urinary tract infection
or a bladder infection called interstitial cystitis
As you have ruled out pregnancy, the other two are quite similar in their presentation, which is why I shall list a few of the most common symptoms out for you, they are:
-Burning sensation while urinating
-Increased urge to urinate, but less amount of urine passed
-Lower abdominal and/or flank region pain
-Itching around the genitals
-Blood in urine or immediately after (not always seen)
As you must know, you do not have all the symptoms, and it is not necessary for all the symptoms to be present in one individual.
Now coming to your urine report, as it was first reported that you did not have an infection, this must have been a urine analysis, which at times can report a false-negative report. I would thus recommend a urine culture examination, which is more accurate and will provide a lot of additional information that will aid in your treatment.
I hope I have succeeded in providing the information you were looking for. Please feel free to write back to me for any further clarifications. I would gladly help you.