Anyone out there using the Rock n'Play for their baby? If so, how long did your babe sleep in it? Are you worried about flat head? Mine is 6 weeks and loves sleeping in it all the time. He sleeps in it at night and for some naps throughout the day. We put a bit of cushioning in it but I'm still worried about flat head. I'm also worried about transitioning to a crib since the sleeper is on an incline and wondering if he will get used to sleeping that way. Any feedback would be much appreciated!