What Causes Labia Area Splitting, Tenderness With Blisters?

I am splitting in the labia area of the vagina. It had become bigger and more tender over the past few days and now I have blisters in the folds. I recently took three different antibiotics for a 2 cyst and strep throat. Is this a severs yeast infection? I have three children and have been tested numerous times for STD's, so I wouldn't think it could be that.