Baby sleeping with face down

My baby rolls now and he prefers to sleep on his belly (will absolutely not sleep on his back anymore), but he’s been sleeping With his face down on his arms . This makes me really nervous that I’m up and down all night checking on him. I’ve tried to turn his head but he turns it back to face down. He sleeps in a pack n play in mine and my husbands room and the mattress isn’t think but it still worries me . Anyone else’s baby do this?