Breast feeding help, please!

I don't know if I'm making enough milk for my baby. She lost nearly 12 oz. In seven days. I have to take her to get weighed again tomorrow to see if she is gaining weight. I have been EBF, and she seems pretty content most of the time. She does have wet diapers and like 3 or for pooped diapers a day now. I try to pump, and like literally nothing comes out. When I hand express, pretty much nothing comes out. I am so concerned. I want to breast feed so badly, but I fear something is going on. Especially since I pump like 5 drips per breast in 10 minutes of pumping. I have to go back to work in about 4 weeks, and pumping is the only way it will work.