Current down comforters are chambered so the down can’t all move to one side or another. However, until you get a new one you should shake the comforter a few times (fluff it) as you are making the bed to redistribute the down that has been moved during the night. Don’t wait until it all bunches up to do it or you will be working a lot harder at it if you do. An easy way to fluff up the comforter is to put it in the dryer with a clean tennis shoe or tennis balls, that will work air into the comforter and redistribute the down and freshen it up a bit too.