Other option. Despite pumping frequently at work you may not be a pump all the milk your infant needs to sustain good growth. To make up for this i tried pumping on 1 breast while nursing on the other breast 1 feeding per day to store extra milk and increase supply. You may also have to consider formula supplement if you can't keep up, which i also did. Discuss with your pediatrician what is best for you.
Try this. This can be very frustrating as a working mom who is trying to breast feed. I personally found it hard to pump between patients. What i did was pump on a double electric pump as soon as i got to work for about 10-15 minutes, then for a full 20 minutes at lunch, and again for about 10-15 minutes at the end of the day prior to leaving for home.