I know each baby is different, but DS is 19 weeks today and still hasn't rolled over. He does roll to his side and sleeps like that most nights now, so that's progress. I try to help him out with tummy time or give him a little nudge, and he won't have any of it. He prefers to be on his back...I think he's just lazy!

Should I be worried or doing anythign differently to help him along? I'm not that concerned about it, but I keep getting emails from The Bump and BabyCenter saying it should have happened by now!
Re: 4 1/2 months and not rolling yet
Since he's not even five months yet, he should be alright. My little lady is just now starting to roll from back to tummy (she does it from tummy to back, but even so, she does NOT like tummy time). Maybe by six months would be worrisome, but otherwise all is likely well.
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