Very itchy vagina

for about 5years now iv had a very itcy virgina on the out side the best way to discribe it is like atlete foot once you start you cant stop i itch that much the skin comes of and leaves me red raw, any creams that i use burn me as its an open wound

i dont have any unnormal discharge and it doesnt smell

iv been tested for std and im all clear also been tested to see iv im elerjick to anything eg washing powder and that came back clear please please can any once give me any adivce on this as its making me depressed

thanks