Hello Sahar and thanks for the query
You have pus cells in your stool which indicates that infection still persist that's why you are getting symptoms back. Your doctor is right, you needs more antibiotic for getting rid from it. But which one so that you wont get it again?
In my opinion you must go for stool and urine culture examination as you are getting pain in kidney
also. Start your antibiotic according to the culture report so that you get the antibiotic which is effective on that bacteria.
Take high fiber diet and keep yourself hydrated.
in case of fever
Hope this will help you.