why my 3 1/2 month baby weight is not up to the mark of WHO standards even also I am breastfeeding her for every 2hours

A. See the child should gain at least 500 g in a month and for first 60 days you are supposed to feed your child every two hours after that it is supposed to be fed on demand yet if the child is not gaining weight then maybe your breastfeeding is not enough you may check with your doctor and if they suggest you can start with formula milk