Flat spot on one side of head..?

ok so i have a 3month old baby gurl and she has a flat spot on the side she favors to sleep on. I cant get her to move it to the pther side. I have swiched the way she sleeping the crib and i give her as much tummy time as she wants....She naps on her swing and sometimes in her bouncer...When she falls asleep i move her head so she sleeps on the side that isnt flat but by morning she is back to the bad side...What do i do to fix it? When will it permintly be that way? and how do i mold it myself like in the olden days?