hi there, do not stress yourself by comparing your baby with others I feed my baby on demand, as and when she wants it (she is 4mths plus). I dont't keep track of what time I fed her. I dont't wake her up to feed when she is sleeping.
Did your child's pediatrician said that he is underweight? Because usually, different docs have diff ideas of what is underweight. My 2nd daughter weighed less than my nephew at 8mths old and yet my nephew's pediatrician said he was underweight when my child's pediatrician said she was developing fine.
As my child's pediatrician said, nowadays, it is very rare to find a malnourished child in singapore. Your child might just be on the small side