Is this a valid reason to go to the ER?

It may be a yeast infection and pills don't always work right away, if at all. I would suggest you drink cranberry juice, eat yogurt and only use baby soap down there (certain ingredients in soaps can cause irritation) for the next few days. If it's still bothering you then make an appointment. and just to let it get plenty of air. wear skirts and cotton or lace underwear if possible.