Try weighing yourself every hour. I have to stand on a scale every hour to hang a material bag above. Thus, I see my weight every hour. I typically see fluctuations of about 3 lb throughout the day. I drink a lot of water, and thus eliminate a lot of water often as well all day long. Couple that with 115° temp on the plant floor and I sweat buckets also.
How about clothing when weighing yourself? Same clothing (or lack of)? I weigh 4-5 lb heavier at work from clothing. Plus I carry almost a pound of items in my pockets.