UTI for almost 2 weeks..help!

Hi everyone,
I have had a mild uti for the past two weeks (mild because there is no burning sensation when I pee..I just need to pee ALL the time and sometimes there discomfort in my lower abdomen) so I went to the doctor and he did a dipstick test there and then..nothing came up but from the sounds of my symptoms he said it sounds like a UTI so he prescribed me Kelfex..that hasnt helped I still need to pee literally 10 mintues after I go and I still have discomfort in my lower abdomen. He gave me another repeat so I went and got some more..its really REALLY irrtating and uncomfortable..anyone have any suggestions on what I should do or what it may be instead?