What Causes Painful Infected Blisters On Vagina?

Hi, I've been having terrible vaginal irritation, at first I just thought it was a yeast infection, which is not uncommon for me. I used asodopholus and ate lots of yogurt. When the irritation increased, I started seeing ulcers which started to bleed. This was the worst pain I've ever been with.
I've only had sex with two guys, who both claim to be clean.