What Causes Vaginal Irritation With Urination Burning Sensation?

I wake up in the middle of the night with vagina irritation and it burns when I pee. I have been to the doctor and my pee tests came out good. This has been going on for 2 1/2 weeks and I can t take it anymore. I have to drink up to 12 water bottles a day for me to feel better. Also, pain relievers don t make me feel better. What should I do ?