Hi A.,
I breastfed my two biological children for a year each. What really worked well for me with my youngest was to pump every day at the same time, a time in-between feedings. With my oldest son I had one helluva time trying to pump enough milk to feed him, and he wouldn't touch a drop of formula, so it was a nightmare! Then I was lucky enough to read somewhere when I was pregnant with my youngest that if you pump every day at the same time it will trick your body into producing an extra feeding's worth of milk at that time. Sure enough, it worked like a charm after my youngest was born (8 oz. every morning at 8:30, after the breakfast feeding), only I stopped after I had a freezer full of milk and then later, when I went back to work and needed to pump again, I wasn't getting nearly the same amount (maybe 4 oz.). So now I know never to stop, even if you have to discard the milk at the end of the day, because you never know when you're gonna need it later.
Are you using an electric pump, preferably a double? I tried a couple of hand-operated ones, but what really did the trick was the Ameda Purely Yours electric double pump. Scary looking, yes, but effective, even better than the Avent pump that everyone raved about. I feel electric is most definitely the way to go.
You say you can only pump every three hours at work; how often do you nurse the baby when you are home on the weekends? If more often, then try to match your work pumping schedule to what your baby's nursing schedule would be. Your body will only produce more milk if you offer more stimulation; if you can manage to match your pumping schedule at work to the nursing schedule at home, you should have more success. It's the law that your employer has to allow you to pump at work or it's discrimination; if you need more time to pump, definitely take it if you can. Your employers have to provide someone to cover you if you need it.
You say you can't pump on the weekends because he is nursing all the time. That is natural, because he misses that special bonding time with Mommy. Definitely try to get that extra pumping session in, though (the one I mentioned earlier). Find a time that works for you (preferably one that matches the extra pumping session you are doing at work) and be consistent. It will take your body a little while to get used to this new pumping, and for the first week or so you might not get much milk at all, but eventually (God willing) you will get a real feeding's worth of milk. After that just remember to keep up the extra session No Matter What and you will have that much more milk to send to the daycare on Monday mornings.
I have heard good things about using beer like Dianna mentioned also. I never heard of using non-alcoholic--just drinking half a beer (and no more!) in the evening--but I have heard that small amounts of beer increase milk production. One idea I heard was to find a friend who is also lactating if possible and sit down with her a few times a week in the evening to split a bottle of beer. Apart from the benefit of increasing your milk production this also allows you to relax with a friend in a similar situation. Relaxation is always good for us stressed-out moms, especially when we have teeny-weenie babies.
And finally, if all else fails, don't feel bad about giving him some formula. I never liked formula either, and I felt like a big failure when my husband and I eventually had to give my youngest a bottle or two of formula every day. However, I was the only one who felt that way! My mom, mother-in-law, husband, and son's pediatrician all felt that the baby was fine and healthy, and that the formula was the best thing for him when my milk supply waned. (Unfortunately, my electric pump broke AFTER I stopped doing my 8:30 extra pumping session and it took me a few months before I got a new one; by that time, my milk supply was down because the Avent pump wasn't working well.) But the baby was fine with the formula, and I still nursed him three times or so during the day and the same at night, so there was no need to feel guilty. Just remember as long as the baby is happy and healthy you are doing a great job.
Good luck, and if you get a chance let me know if any of this was helpful.
--M.
P.S. If you ever have another baby, now you'll know to start that extra pumping session every day after you get your nursing routine established. I know if I ever have another baby I will!