D.C.
Assuming your baby is nursing and not acting hungry, it may not be that your supply is low, but that your body isn't responding as well to the pump and so you are not getting all the milk out.
One thing that helped me pump was to close my eyes and imagine that the baby was actually nursing, at least until I got that 1st letdown. Some people look at a picture of their baby while they pump.
Another thing is to experiment a little with how you are pumping. Some people get better letdown if they pump for short periods of time, more often. I actually got more milk by pumping longer - if I kept the pump running, I would have a 2nd letdown of milk about 15-20 minutes after I started. One woman I know did this buy pumping about 10 minutes, then turning the pump off for 5 minutes, then restarting it to get the 2nd letdown. If you have enough time in the lactation room, you could try this.
Also play with your settings. More suction on the pump doesn't equal more milk. If the pump is set too high, it can start to become painful, which doesn't let your body relax enough to release the milk. Play around with your pump settings until you find one that is optimal for you.
Make sure you are drinking enough water. And yes, the stress over the weekend can affect your supply. Hopefully this week will be less stressful and that will help a lot.
Good luck!
Added: Also, when I was nursing and working, there was a wonderful group of women in a Yahoo group: BFWorkingmoms I don't know if the group is still active or not, it's been a year since I was on it (baby is weaned now). But they were a great source of advice on breastfeeding, working, and pumping from women who were doing it.
