Vaginal Perineal tear

I have been plagued by small cracks between my anus and vagina that usually turn into small circular sores that burn like fire if I get urine on them or even move the wrong way and stretch the skin. PLEASE help. I've gone to the doctor. He says its probably fissures and just to put polysporin on them and try to keep the area clean. I do. I carefully wash with physo-derm. I blow dry with a hair dryer--carefully so as not to burn it too. Lately I've taken to sitting in the hot tub about 2 or 3 times a day too. What is going on????????? Yes, I think sex probably is causing it, but not always. Please tell me I'm not alone with this. I've been treating this episode for about 12 days now and it is not getting better.