M.R.
I exclusively pumped for 3 months and used a variety of techniques to up my production:
-How long are you pumping? I would pump for at least 15, sometimes 20 minutes each session, 7-8 times a day.
-Drink, drink, drink lots of water. While it isn't the amount of water that makes the amount of breastmilk, you do need to stay hydrated so that your body can keep up with all the extra work you're asking it to do.
-Oatmeal! Have oatmeal for breakfast because there's something in it that can help with milk production.
-When you pump make sure you drain the breast. You can tell when it goes from streaming to dribbling to almost nothing. Pump a few minutes more after you get to the 'almost nothing' stage. By doing so, you send a message to the brain "Hey...we need more milk here! Let's up the prolactin and get busy!"
During my pumping sessions I was getting plenty of milk to feed for the day and bank anywhere from 8-16 ounces in the freezer. I was able to extend my 'breastmilk feeding' to about 5 months after I stopped pumping at 3 months.
Finally, if for some reason you are unable to make enough milk do NOT beat yourself up over the fact that you may supplement with formula. When it comes down to it, your child has to eat so if formula is the last resort and you have to make that decision do not let yourself feel guilty about it or as if you have failed your child. I can assure you that your child will not be ruined or compromised because of it.