my nephew is preterm born at 35 weeks and,weighted 1. 86 kg. he looks very thin. looks like how he looks when he was born. currently he is 2 months old he is,2. 4 kg . he has not gained weight from last 15 days. is that weight ok. qe are extremely worried about his health. he cryes a lot always. and fussy always. should we,take any extra precaution and consult doctor immediately . thank you so much