What Could Blood In Urine With Pain In Flank Region Suggest?

I have bouts of severe pain in my left flank, I have been having this problem for about a year. It seemed to start after I had a kidney stone. I have since passed the stone, and have had numerous CT scans which all seem to show nothing. I seem to always have blood in my urine when they do the urinalysis at the ER. Does this sound like I could have lphs? The ER doctors always seem to think I am making up the pain, but it is very real. Please help, I am at a loss.