Indeed, expect your weight to fluctuate from hour to hour, and day to day by several pounds, what's important is the long term trend, not the immediate measurement. If you just think about how much water and food (and the "results") that go in and out of your body during the day, and how much that all weighs, it's understandable why this would be the case. A large glass of water (a pint in UK terms) weighs about a pound, so just drinking that will increase your weight.

I wrote a more detailed post explaining what happens which is probably worth a read.

In short, don't worry about the small changes of a pound or two, concentrate on the long term. I don't know about you, but I'm trying to lose weight not for next week or month, but for next year, and all the years that will (hopefully) follow.