Has anyone had issues with their baby gaining weight? He was born 10lbs 2oz and lost 2lbs right…

Has anyone had issues with their baby gaining weight? He was born 10lbs 2oz and lost 2lbs right after birth and now he only weighs 12lbs his dr had me switch his formula to similac neosure which is for premature baby’s to help gain weight it’s helping a little bit but not a lot he only drinks 2-2 1/2oz every 3 hours and will eat 1-1 1/2oz in between feedings (I have tried doing a schedule and he still only eats the 2-2 1/2 oz). Any advice would be appreciated!