PLEASE HELP- FOR THE LOVE OF GOD PLEASE HELP

my child is just now three weeks old and NEVER gets full. He literally just ate 5 oz of formula and is crying for more. WHY IS HE NEVER FULL? Any suggestions? Or anyone know what could be the cause of him being a bottomless pit? I feel like it's not healthy for him to eat that much. I stopped breastfeeding bc he would nurse for hours and never be satisfied and now that I'm bottle feeding in still having the same problem. ILL TAKE ANY ADVICE I CAN GET