It's quite common not to see any weight drop in a week--or sometimes even see a small gain.
Weight loss doesn't go in a straight line. Stay with your program, and you may see a bigger drop next week that will make up for it. Don't be discouraged! Weight can sometimes change a few pounds just in a single day.
You might try weighing every two weeks, or even more, instead of once a week--that way you're more likely to see a drop, assuming you stay on your eating program, whatever that may be.