S.,
Here is a feeding guide I found online. I have a 4 month old and he has been eating like a piggie ever since he was born, he is now on 8 oz. bottles every 4-5 hours! Just watch your son, he will let you know when he wants more food...good luck, it does get better with time!
On average, a newborn consumes about 1.5-3 ounces (45-90 milliliters) every 2-3 hours. This amount increases as your baby grows and is able to take more at each feeding.
At about 2 months, your baby may be taking 4-5 ounces (120-150 milliliters) at each feeding and the feedings may be every 3-4 hours.
At 4 months, your baby may be taking 4-6 ounces (120-180 milliliters), depending on the frequency of feedings and his or her size.
By 6 months, your baby's formula intake can be between 24-32 ounces (720-950 milliliters). This also depends on whether you've introduced any baby food.