Answer:
I am bought by the yard but worn by the foot
I may be of the eye, in order I am pie. In my center there is a star, I keep medics where they are. What am I?
Light hides me and darkness kills me. What am I?
I have an eye but am blind, a sea, but no water; a bee, but no honey; tea but no coffee; and a why, but no answer. What am I?
Everyone has me, but nobody can lose me. What am I?
No matter how little or how much you use me, you change me every month.