Severe Flank Pain

Long story short:
About 6 months ago i started going to the washroom 2-3 times during the night
About 2 months ago it progressed to 4-6 times a night
About 2 weeks ago it was accompanied with pain, as if id been holding my urine for too many hours, it was prainful, and the pain was there every time (all 4-6 times) that id wake up.
Been to a urogynocologist and she tells me i have an overeacctive bladder - no i dont, it only happens at night, and the pain has gotten worse
I was foced to the go to the ER two days ago b/c the pain was so bad i just want handle it, its severe flank pain and lower abdomen, i guess around the bladder.
Im a 24yrs old female and i cant even stay a full day at work cuz the pain is so bad.
Done ultrasounds and CT, and nothing shows up.  ER doctor told me that although nothing showed up, he knows that smth is wrong with my urinary system...
someone help?!!!
btw, neither advil or tylenol do so much as alleviate the pain :( im miserable