So my 4 month old twin boy has been rolling to his side for a few weeks now. Just the other night I…

So my 4 month old twin boy has been rolling to his side for a few weeks now. Just the other night I saw that he was doing it in the crib at night now when he sleeps. I'm worried because he still does not have the best head control or great core strength. But it has gotten better then it was a few weeks ago for sure. So do I need to worry or not that he is sleeping on his side with the notion that he could flip onto his belly and suffocate? My twins sleep in the master bedroom with me so they are not alone at night.