What Causes Vaginal Sores With Itchiness And Burning Sensations?

I am a mother of three aged 37 years, I weigh 80kg and my hight is 1.8meters. I have for almost a year been havinh viginal sores.I have been to doctors and was given antibiotics and viginal creams and these have not been helpful.These sore keep going and coming back and are itchy but I rearily get burning sensation when I urinate.A test for STDs was negative. I have tried salt but has not helped.