How much? HeLp!!

How much is to much for a 2 month old baby to eat? My baby eats 6-8 oz every 3 to 4 hours and if I try to feed him any less, all hell breaks out but I feel like it's to much. Being a first time mom, I dont know what to do. His doctor said 8 oz might be to much but sometimes if I dont give him that, he screams. On top of everything he refuses to sleep almost all day till about his last feeding around 9-10 PM and then he sleeps almost through the night till about 4 am