What Causes Itching In The Vagina?

For several days I have been itchy and sore in the vaginal area. The left labia minor has gotten increasingly redder and more swollen. It ias about twice the size of the right labia. and it is very sore in the crease next to the labia. I also have a white discharge at times from the vagina. The whole area is itchy and red. It hurts to have underwear on! Can you help?