The best way to increase your milk supply is for baby to breastfeed, frequently. Obviously she hasn't been able to, but you might ask what the BF policy is for when she comes home. If you can breast feed her regularly, your supply will probably increase alot. If you can only BF her a couple times a day, you will need to keep pumping. The pump is not a great substitute for BF, but for us preemie moms, it helps, and is pretty much our only option.
I drank decaf rootbeer (most is decaf, but always check the label), which seemed to help a little bit. But it isn't a substitute for bf. Keep at the pump, frequently, and when Jasmine is home nursing it'll probably get better for you.