afro on "Can't pump enough milk because DD eats around the clock"

Hi!

I'm at a loss on how to pump enough milk for my DD. She is 5 1/2 mos old. She just eats around the clock, always has. Here is our schedule:
7:30a - breastfeed
9:30a - bm bottle at daycare
11:30 - bm bottle at daycare
1:30p - frozen bm bottle at daycare
4p - bm or formula bottle at daycare since I don't have enough
5:30p - cereal
6:30p - breastfeeding
10:30p - breastfeeding
1:30a - breastfeeding
5a - breastfeeding

I pump at 9a, 12:30a and 3p, but I'm still short a whole bottle. She eats 5-6oz bottles and I only pump 3-4 oz. I've been pumping around 7pm to get some extra milk, but I have to take care of my toddler, so that is no longer an option. Should I be able to pump more milk at work? I pump for 15-20 min and don't get any work done as is, so I can't pump any longer.

Any ideas?

Thanks, Rita