I have naturally medium brown hair, and ive had it highlighted for quite sometime. Right now, its mostly a medium blonde with some brown streaks. (plus about a half inch of regrowth) But anyways i want to die all of it blonde. A light blonde like Jessica Simpson. I bought a box of Clairol born blonde, but I know that since my hair is already blonde,the blonde will just get blonder and the brown wont turn blonde enough. What should i do?