Weighing infrequently is good because it keeps us from freaking out at random noise that can happen due to fluctuations in water. But it's also bad, because if you happen to be a bit high or low on water on the rare weigh-in, the ability of random noise to give a false impression gets inflated.

Same question Janet asked, but what does gaining 2 pounds mean? Are your stats up to date, did you originally lose 10 pounds and gain back 2?

One thing that I find can affect the scale when I'm doing one meal a day is the time of day. If I eat early in the day, I'll weigh less the next morning than if I eat later in the day. If I weighed myself while eating three meals a day, and then switched to the same calories, but all at dinner, I'd probably weigh more the next morning as well.