I have been having pain in my kidney areas (aching type pain), then it starts to hurt in my bladder and urethra (this is a more sharp pain) . I urinate frequently and cannot hold my urine. I have tested negative for a bladder infection and did an ultra sound that found nothing and they did not find any stones in my kidneys (the ultra sound took place about 2 weeks after the onset of pain). The pain lasts for about 1-2 weeks then goes away and comes back a few weeks later. Any ideas what this could be?