Quoting gonzalez10:" i know how you feel. at my daughters 4 month check up the dr said one of her legs was longer than the ... [snip!] ... i wonder why they dont keep their comments to themselves if they arent sure...or atleast reasure us that they could be wrong!"
At our 6 month check up the Pedi told us that if they weren't rolling over and sitting alone by their 9 month, that we'd have to be referred to specialists. 9 months appt came, and they were rolling, but not sitting alone (for longer than a few minutes yet), and he didn't mention anything at all about the specialists. He can use both arms to push up on, so it's not like he can't use it.