Anyone else’s baby doing this too?

My 4 month old has mastered the skill of rolling onto his stomach and he’s very excited about it because he does it all day. I don’t mind when he rolls on his stomach for naps but at night I freak out. I noticed that sometimes he likes to sleep with his face straight down on his mattress and he doesn’t move his head to the side! I know he knows how to roll from tummy to back too but it’s like he forgets and starts crying because he’s getting tired of lifting his head on his tummy. I freak out so bad and move his head. I guess Im nervous because I feel like he’s so young still and everything Im reading says it’s safer when they’re 6 months to sleep on the tummy. I have a monitor for him but sometimes it’s hard to see if he’s breathing.

First time mom here so I might be over reacting but it just scares me a bit.