The average weight for a baby boy of 3 and a half months is 6.5kg.Your baby's weight is definitely well below this expected weight and his weight is in the lowest 9% for baby boys of his age. He seems to be taking enough formula for his present weight, but below the necessary amount for his expected weight. It is possible that his recent infections have set him backa bit with regards to his weight gain as well as his milestones.Give him another 4 weeks or so to see if his weight gain improves, if it does not it would be best to ask your paediatrician to see your baby just to make sure that all is well.
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