Help Me Please!!!

So recently my son who will turn 11 months pretty soon is starting to sleep on his tummy at night. I'm always waking up every minute to check up on him to see if he is sleeping on his tummy or not, & when he is I'm always flipping him so he can sleep on his back again. He never slept on his tummy before so this is new to me and it scares me because I'm afraid he won't be able to breathe if he doesn't moves his face to the side. I was reading about this breatheable mattress and I was wondering if any of you ladies bought one for your little ones? & if so is it worth buying one? Sorry if it's long just need some advice on this one.