Suggest Treatment For Burning Sensation In The Vagina

My question: I have vaginal burning only. No other symptoms. For about 2 months now. I took diflucan & flagel, but did not help. It also burns when I urinate. But think it is from urine hitting vaginal opening. I had Std testing done in April and all came back negative, including a urine clyamida test. How accurate are the std urine tests? My boyfriend is not having any symptoms & he promises he hasn't cheated. And I know I haven't. What could be the problem? Thank you!