You probably shouldn't be trying to lose that much weight that quickly. It's about 2lb a week is the general recommended amount I believe. Takes no time to put weight on, but takes a long time to take weight off in those circumstances.
As for the person who said they were losing weight even when eating thousands of calories, might want to go to the DRs and just get checked out. unless you are doing lots of exercise you certainly shouldn't be losing that much weight.