my baby is 50 days old. he is completely breastfed he has gained only his birth weight so far. he has urine output of 8-10 but still not gaining weight.. is there any specific reason?

A. hello baby should be gaining a minimum 0f 150 g to 200 g per month.. babies birth weight will first reduce and then starts gaining and if the bm is not sufficient then give baby infant formula milk stage 1 using a bpa free bottle like Babyhug which can be helpful