Yeast infection

So I’ve had this yeast infection for going onto 4 years and it won’t freaking leave! I’ve gone to multiple doctors and they don’t know why. They’ve tested me for everything and the only thing that comes up is yeast infection. Please tell me there are others who have gone through this and is there anything that helped you? I don’t douche, year tampons, I sleep naked, mainly wear cotton underwear, don’t put anything w fragrance near down there. Please help!