My weight goes up midweek every week for some reason. But it doesn't stop me from weighing too often. I just know that my honesty with my food log means it's not anything to worry about.
I weigh my lowest, like a lot of people early in the morning...by the end of the day it's not unnormal for me to weigh 3-4 lbs more than my morning weight. When I get up in the middle of the night, it always drops some...
Body rhythms control some of this. Do your "official" weight however often you need (I do mine once a week), journal it, and know if you are being honest with your plan, the numbers will go down.
(Of course this still doesn't stop me from weighing too often. But then, how else could I fret about my midweek bloat?)