New Weight Loss Plan

I woke up yesterday morning and was reasonably happy with my weight.
I went to the gym and ran 2.5 miles then did an hour of pilates.
I came home and stepped on the scale and gained 2 lbs. Hmm.
I was mindful of what I was eating throughout the day and didn't snack, other than a Slim-a-Bear Klondike 100 calorie ice cream treat, after dinner.
I weighed myself before bed and found that I gained another 2lbs, for a total of 4 lbs.
Then I woke up this morning and weighed myself . . . . and I LOST 5 lbs!
I'm not a math or fitness expert but if I gain weight while being awake and lose weight while sleeping, shouldn't I sleep more?