Hello! I have a 4.5 month old son who still isn't rolling. He can roll from his back to side (and stay there), but can't roll over from tummy to back. He's never really liked tummy time, but we persist. He's also a REALLY big boy (in the 100th centile for height and weight). He's 100% breastfeed, he's just a big, tall lad, and this seems to make it much harder for him to shift his weight or bear his weight on his arms. He's hitting all his other developmental milestones and is a very chatty, social fella. Should I be worried at this point? Thanks!