LOW CENTER BACK FLANK PAIN, CONTINUING TO GET WORSE

PLEASE HELP - I have what I thought to be a UTI and went to the ER with symptoms of low flank pain (center) and burning/urgency in urinating. I was told I have a UTI and given Bactrim. My low back flank pain has continued to get worse, almost debilitating. I went back yesterday and saw my DR. and she told me that I had no sign of a UTI and that they thought it might be muscular. I have been doing nothing that would cause muscle/back pain. Before the UTI I was on an antibiotic for an ear infection, then approx. 3 days later I started getting the UTI symptoms. My DR. told me there wasn't anything more she could do for me!!?? I have been told that I have gallstones and they think this might possibly be related to my pain, so she told me to go and see a gastroenterologist.
My main symptoms are low center flank pain, urgency to urinate and when I urinate I can hear what sounds like gas coming out of my vagina and little bubbles are in my urine.
PLEASE any suggestions on what to do next would be most appreciated. I am in the VA system, and whatever 1 DR. says, the rest go along with, so I believe they will no longer help me, at this point.
PS I was also taking D-mannose for the UTI, would that have been a reason why the urine test came out negative?
Thank you.

[Dr Santos]

Hi,
How are you? What other symptoms are present? It is good that the urine test was negative, this could indeed rule out presence of an infection. Other differentials may include muscular spasm  or gynecological issues.  Warm compress, rest and pain reliever may help provide symptomatic relief if it is caused by muscle issues or referred pain from the gallstones. However, if it persists, you may also need to see your gynecologist as well as the gastroenterologist for further evaluation. Imaging studies may also be indicated.  Take care and do keep us posted.