Hi , I'm Getting Urine Burning Sensation Regularly. Like Once

Hi ,
I'm getting urine burning sensation regularly. like once a month.. twice a month..
but after im taking this citrilka liquid and norflox tablet it's getting recovered. now I'm using this medicine during last 1 1/2years when I'm getting the burning sensation.

What I want to know is , why I'm getting this infection time to time?

last year I consult a uriologist doctor and he had done all the medical checkups which related to kidneys and urinary system but all reports wear normal.