Recurrent infection. Permanent solution.

Hi I m having recurrent urine infection since 2 years some times my urine reports are normal but still having burning in urine so many times I had taken antibiotics after finishing my course I had a relief but after some days it happens again last time my culture report shows ecoli bacteria so I get antibiotics and get relief also but after 1 month I m having again same problem but at that time urine reports are normal I m getting frustrated what should I do .mostly it happens after protected Intercourse we change our protection brand also as my dr.suggested but nothing will change , even my diabetes and usg reports are also normal but burning and pain in urine history still here . Plz suggest what should I do I visited gynecologist also but nothing change plz help me with permanent solution.