Hiya, normally uk doctors put you on a five day course, go back to your doctor and tell him, i have kidney and bladder problems and i am always on five day tablets and if they dont clear it then another lot and if that doesnt clear it well with my problems i normally end up in hospital... however it sounds as though you need to go back and see him hun in case the tablets were not strong enough to clear it..
or you could go to chemist and buy lab sticks and check for infection yourself, but to be honest if your new to kidney pain, then i would head back to gp