B.,
It looks like the others on here have provided you with a lot of information, but I just wanted to add to it.
I actually felt the way you did when my son was a newborn, so I went to see a lactation consultant at "The Nursing Station." They were really helpful. They weighed him just before and after he ate to see how much he was taking in...by the ounce. They are off of Dupont Circle and their number is ###-###-#### if you would like to contact them. I also went to see them because even though I do not have inverted nipples, they were so small that when he would go to latch on, they would invert. After a month or so of using a nipple shield they were fine.
Also, someone else recommended using Mother's Milk Tea. I have heard that is a great product. So if you come to find out that you really are not producing enough, then I would definitely try that.
I wanted to point out that I do not drink a lot of water, I hate water! I try and get my fluids from non caffeinated beverages, like lemonade and decaf tea, stuff like that. I still don't drink enough and my supply is fine. It could just be me though...also, I have been told and read that if you use a double breast pump and pump both breasts at the same time it stimulates more oxytocin whicn in return creates more milk.
The last thing I wanted to mention is that you should check out this site http://www.kellymom.com/bf/supply/index.html
It is a great website for nursing moms and will likely be able to answer any BFing question that you will ever come up with.
Good luck, hope I helped!
T.