Can't pump enough

I'm currently nursing but trying to build a stash for when I go back to work at the end of January. My girl is one month old, so I should be at the peak of milk production. She is a great nurser and is actually gaining weight a little too quickly (per the dr). So I know I make plenty of milk. The problem is my pump doesn't seem able to express it. I pump twice a day, once at the first morning feed and again at the late morning feed. I pump one breast while she nurses the other. I only get at most one ounce when I pump, and sometimes only 1/2 ounce. And after pumping I'm able to hand express plenty more milk from that breast, so the pump is just not emptying my breast as well as my baby can. I have a Medela pump in style. I've tried heat application, lowering the suction, new membranes on the pump, different sizes of phalanges for the perfect fit. I need help :( I've been pumping over a week and don't even have enough in my stash for two feedings. Any other ideas?? I see these pictures of huge stashes and I only have 6 ounces in my freezer :(