baby is 2 month 5 days old. She is rarely drinking milk, in a day app we are trying to give 4-5 times, in that also she is drinking very less and refusing to drink further or sleeping. currently feeding only mother's milk. rarely giving formula once per day. and not sleeping properly in night. Also her birth weight was 3.7 kg. and current weight is 5.5kg. is it a concerning thing? how to make her drink milk regularly?