What Causes Vaginal Itching, Burning, Discomfort And Discharges?

I dont know what I have. I thought it was a yeast infection, but after Canesten, a few doses of fluconozole, garlic pills and acidophilus supplements nothing works. I got swabs done for yeast and stds but all were negative. I am in severe discomfort with extreme itching, constant burning, and lots of discharge. My next gyno appointment isn't for another 6 days. What could I possibly have? (18, female)