E.R.
A pump is not as good as baby at keeping up milk supply, so that probably is why you are struggling - and stress too. Is it possible for you to actually nurse her for any of the feedings? That would help, I think. I am also trying to increase my milk supply right now and was given instructions from a lactation consultant to "power pump" - two times a day for one hour each time, pump for ten minutes, take a break for ten minutes, then pump for ten min. until the hour is up. Don't look down b/c you don't need to be concerned about how much is coming out - you just want to give your body the message that more milk is needed. Also, this should be done after a feeding, so for you, immediately after a regular pumping session. Also, keep the pump on the lowest setting to avoid injury. You do this for two days in a row.
The LC also said to drink Ovaltine 2 times/day (the original kind) or non-alcoholic beer, and sprinkle sesame seeds onto food. Good luck!