You probably have a yeast infection. I would go see the doc asap and he / she can give u something to make it go away. Its a common infection and can come from just wearing tight pants.
One common cause would be a mild yeast imbalance. You should probably go to the doc and be checked for yeast. Diflucan is a very effective tablet by Rx. Or take Azo-Yeast, 2 pills a day while reducing dietary sugar and carbs and increasing vegetables. Use a very mild soap, like unscented Dove. You could use a topical yeast medicine, but they have ingredients that irritate a lot of women.