Pain in lower back & left side, vaginal itching, swelling & burning . no discharge or odor. dr.did test 4 uti 2 wks ago, was negative. what can it be?

Few possibilities: It appears that you have seen your doctor. Left flank pain may indicate a kidney problem therefore I suggest a sonogram of the kidneys. Itching in the vagina is generally due to candida infection. There is no harm in trying a course of over the counter Monistat7 vaginal cream. Stay in contact with your doctor and tell him about my suggestions