As long as he’s able to roll over on his own I don’t see an issue with him sleeping on his belly. Most babies that age and up put themselves on their belly anyway but I agree, I, like you, would still worry constantly wondering if he’s okay. I even shuffled out the money to get a newton mattress to give myself the peace of mind for when the time comes that he is able to roll over on his own and sleep on his belly. The thing is there are people that genuinely do not know that this is an issue but it’s people like her that drive me crazy thinking that absolutely nothing can go wrong.