My son (now 6 1/2 months) has been on 7.5 MG daily since the age of 5 weeks.  He doesn’t seem to have any issues with fussiness though - even with teething.  At his last ped appointment a couple of weeks ago he was in the 50th percentile for height and 40th for weight.  He was very low for head circumference though, only the 10th percentile.  The pediatrician was not concerned, but has anyone else experienced this sort of disparity?