Just to share my expierence....my son is now 11 but he was a very slow weight gainer and a very slow heighth grower. He's just now started to catch up to the boys his age, but I'm saying just now within the past 3 months. He's gained 15lbs in 3 months and grown 4 inches....allllll of a sudden too! No worries because his doc monitors him but it took him 11 years to get to this point I was "talked to" by people all the time because he was always much smaller weight/height then kids his age. For example when he was in 1st grade you should averagely wear 7/8...he was just starting to fit into 5/6 pants if he had a belt.....

I think as long as your doctor says your lil one is fine...it's good.