Suggest Treatment For Dark Brown Skin Between The Legs

I've got dark brown skin between my legs, in my inner thighs, it looks like it's really dirty but I do wash. I'm guessing it's from my legs rubbing together and stuff when I walk (I'm a fairly big girl). I just really want to know how to get rid of it! I'm always scrubbing at it, but it doesn't seem to be going away. Does anyone know how to get rid of this?