I suggest you look for a different urologist. You need to have a PCR test rather than a standard urine culture. You need to find out what organisms are causing the problem. Our bladders are not sterile. We normally have a whole host of organisms living in them naturally and normally.
It is when the balance of organisms gets out of whack or another different organism, not normally growing there, starts growing and overwhelms the system the naturally occuring organisms that things get out of whack. Good luck.

Also find a good quality cranberry-mannose capsule and take them according to your urologist's instructions.