Hi! My baby started rolling recently which includes in her sleep, i know it is ok to leave her on her stomach now if she rolls there, but she sleeps with her face in the mattress! Scares me to death! Is it still ok to leave her like this? I usually go in & turn her head. I havent mustered up the courage to leave her like that and see what happens. She is almost 20 weeks old & can hold herself up. Any advice would be appreciated. Thanks!!