Aww mama, don't worry too much, at 4 months corrected age, your preemie is right on track! A few of us with premature babies realized we have to go by their corrected age (actual age minus how early they were born), so your little one is basically acting like a newborn who's just a few months old, and smiling and head control usually come a bit later anyway. But since you're concerned, it's always best to bring it up with your pedia at the next checkup, they know your baby's full story and can give you peace of mind or any guidance specific to him. Preemies sometimes need a bit more time and patience, pero you're doing great by watching and caring!