Answer:
I am asleep when you are awake I am awake when you fall asleep. I can fly but no feathers to aid my flight.
I am an object which is used in baseball during the day I can't be seen at all
I have skin, more eyes than one. I can be very nice when I am done. What am I?
People buy me to eat but never eat me. What am I?
Two in a whole and four in a pair. Six in a trio you see. Eight's a quartet but what you must get is the name that fits just one of me.
No matter how little or how much you use me, you change me every month.