Why me???

There's another reason to weigh in the morning: You lose carbon, water, and all sorts of things while you sleep just through the act of breathing, and since you're asleep, you're not replacing those elements with food or drink. Add all that to the food you eat during the day, and that can account for quite a few pounds by nightfall.

You should be consistent: weigh yourself when you first get up, after you use the bathroom but before you eat or drink anything, preferably naked (or at the least, in your underwear. No need to increase the numbers with clothing.)