my 2 month baby is not gaining weight from birth,, i am feeding my milk only ,, she is active also,, but not gaining weight,, why?

A. Okay so that is very very good that you are giving only your milk to the child but sometimes the milk of the mum is not enough to gain the weight as your child may not be getting sufficient nutrients from your milk as a good quantity but not quality so if you want you can start giving formula to the child