I had the same issue with he pumping. DS was taking 3 five ounce bottles a day. I was worried about supply and spoke to two different lactation consultants. I spoke to the one at my hospital and e-mailed the one available through the Medela website. They both said that they were concerned that he was over-eating. I know this is long, but below is what she e-mailed me. I found it very useful. We switched to a 4 hour EASY so I only need to pump twice a day and DS is still happy with 5 ounces.
Before babies weigh 10 pounds (4.5 Kilograms), approximately, and while
they are still in the early days, and especially if they are playing
catch-up with growth, they may take 2.5 ounces (75 mls of milk per pound
of body weight per day. After the first few weeks or so, after babies
are about 10 lbs., until they begin solids, they take about 570 to 900
mls a day (19 oz. to 30 oz.) according to the recent research by Dr.
Peter Hartmann. This amount does not increase or decrease much. Split
into 8 feedings, this is about 3-4 oz (90-120 mls) of milk per feeding.
Babies will often take more milk out of a bottle, but this is because
they are trying to satisfy needs for food and sucking, and because they
are sucking for comfort, and cannot help but consume milk while doing
so. As babies grow, after the first several months, their growth rate
slows a bit, and they have a more efficient metabolism, and this is why
they continue to need about 19-30 ounces or 570 ccs-900 mls milk per day
until they start solids, regardless of their weight. Some ways to slow
down the amount that the baby is consuming out of a bottle are to use
slow-flow nipples, pace the feedings (so that feedings take longer),
hold the bottle more horizontally, and use methods of comforting the
baby other than food. Examples are these are rocking and walking with
the baby, carrying the baby in a sling or other carrier, etc…Some
caregivers switch from feeding the baby with a bottle to a cup, as even
small babies can be cup fed when the mother cannot be there. Babies
often consume less milk from a cup.
A baby who is fed with bottles may over consume milk from a bottle. This
is a very common problem. This is because bottles flow at a constant
rate, and abnormally fast. Babies can drink ounces over what they need
because they love to suck, and cannot help but get a lot of milk when
they do. In contrast to bottles, the breast flows at an uneven rate.
Babies can suck as much as they want at the breast, and not be overfed,
because towards the end of the feeding, the milk comes out very slowly.
It is well-known that obesity is less of a risk in babies who are
breastfed, and this advantages continues at least into childhood and the
teen years. Some of this is the breast milk itself, but how the baby
receives the milk—by breast or by bottle, is thought to also be important.
Again, this was from the lactation consultant available through
http://www.medela.com. I apologize for how long that is, but it is useful information. The e-mail was actually a lot longer. If you would like, I can forward it to you. Hope that helps!
