God bless you, J., for your commitment to breastfeeding your son! You are giving him a wonderful start in life, even though it is taking a lot of time and effort due to your job outside the home. Good for you!
It sounds like you're already pumping after some of your at-home feedings, which is always good. It's true that a pump doesn't make your body create the same amount of milk that nursing does, and that can be frustrating.
Do you have a quiet, private place to pump at work? Sometimes moms take something that smells like their baby or helps them feel close to their baby while pumping - a sweet photo, a receiving blanket, stuffed animal, a knit hat. Trying to get a more private place, perhaps with a locking door, using a lullaby CD, trying to relax and clear your mind are all helpful. Be sure you're eating well and drinking lots of clear fluids. The tea that's for nursing moms is helpful too. He may be going through a growth spurt and your milk production hasn't caught up yet.
Once he's old enough for a bit of solids, he may require less milk when he's in day care.
I'm confident you'll work this out without turning to formula, and meantime you're giving him strong immunity to all the bugs that are going around! Keep up the good work!
You can also check the LaLeche League website www.llli.org for more ideas on working and breastfeeding. Look under Resources then the section that has Answers.