To be honest it can be a short period of time and a long period of time. My chlamydia I believe was short. Turned into pid in a few months I think . I took zpak didn't work planned parenthood gave me a rocephin shot five days ago still no relief. She put me on doxycycline 200 mg and metrodinizol 1 gram every day for two weeks. I hope to get a dye test. I'm just so sick of this burning and the Infection. It's a severe one too :(
I think you need some more testing done, but since you are on meds, that might be tricky.
Flank pain can also be caused by a urinary tract infection, kidney infection, etc., so don't limit yourself to thinking an std is the cause, especially with negative tests.
Did they do a pelvic exam? A urine test? Or did they only focus on stds?
Aj