What Causes Recurring Burning Sensation On Outer Part Of Vagina?

I ve been experiencing a burning sensation on the outer part of the vagina for more than three months now. At first I thought it was just irritation or a reaction but after going through all the potential irritants I went to a local clinic due to the fact that I was away at school and don t have a regular gyn. They told me it was a yeast infection and prescribed me a three day cream. After finishing it I felt much better but I still had vaginal burning so I went to two other gynecologist for more opinions and they both prescribed the same antibiotic for yeast infections. After taking it I still feel the irritation, although it isn t as bad as it was before it s still annoying and I m so sick of it. I mainly only get the irritation after I urinate especially if I haven t had much water. Normally, the more water I drink, the less irritated it is and I feel normal, but if I don t drink water the burning comes back. Now I m beginning to think the skin is irritated or sensitive or I have some sort of uti or bladder infection. Please help!!