Hi, my baby is 5 and half month old. He was born premature at 30th week with 1.5 kg weight. Now he is 5.5 kg. He consumes 90 ml formula milk in every 2 to 2 and half hour but since last few days he is not feeding properly, hardly 60 ml in 3 hours. He either falls asleep or cries when I try to feed. Is it normal or should I consult a doctor ?