Advice please

My son is 5 in a half months old. He just started rolling from his back to his stomach. He doesn’t turn his head to the side while on his stomach yet so obviously if he turns onto his belly he

Is face is facing down. I don’t take my eyes off him so if he’s in his belly I can help him turn his head so he can breathe. He sleeps in a pack n okay in my bedroom next to my bed. I’m worried if he will turn onto his belly while he’s asleep. Obviously I’ll be sleeping as well. Is there anything I can do to prevent this in the middle of the night?