Talk to Urologist on Urine Infection

Dear Doctor,

In the end of the May, i feel like itching and allergy on my genitals, then slowly i started have burning sensation then pain in my urinary tract, I went to to doctor they gave me anti biotic course for 1 week, my infection got cured I stopped taking anti biotics, and in the mid of June I feel same symptoms again, I went to Doctor again, and he asked me to do Urine Culture , and after getting the report of bacterial infection he suggested me Novidat 500mg 1+1 for 10 days, I followed the course and my symptoms were gone, I visited him he said to continue Novidat 250 mg 1+1 now for more 14 days, because this was my second infection in 1 month. Now when 14 days of 250mg are near completion I am again feeling like symptoms of itching starting and it will gradually converted in to infection as soon as I will stop the medication.

Please suggest me why it's recurring again and again.

Note: doctor suggested me ultrasounds , which were clear. But infection was detected in