What Causes Cuts On Vagina And Perineum Area And How To Cure Them?

I have been tested for thrush and common vaginal infections, but I don't have it according to my results. I had these thrush like symptoms last month with in a week or a few days before my period, now I have it again this month. It's really uncomfortable around my vagina, I haven't been itching down there much at all, but there the skin has split slightly near the hole of my vagina like on the Perineum area. I'm curious to what treatment I could have, the cuts I have are on the Labium area and Perineum area. I am on anti-biotics, as well, my nurse said that this could be a cause of thrush, she even said that I had the symptoms of Thrush, but the results say other wise. Help?