Beth- how much "bouncing up and down" is the scale doing? Are you weighing yourself at the same time each day, in the same amount of clothing?

If you're weighing at different times of the day, the fluctuations are meaningless. I remember once weighing myself 4 or 5 times a day (back in high school when I was 140ish) and my weight would vary 5 lbs from morning til night, between food eaten, when I'd last gone to the bathroom, general fluid retention that lowered overnight, etc. I would guess that the amount of daily variation is a proportion of body weight and the actual numbers are a bit higher for somebody heavier.

So if one day you're weighing yourself after the morning coffee, and another day right before bed, etc, the results won't be accurate. Even if your'e weighing yourself every morning before breakfast, there are still some small variations that have nothing to do with body fat. If you're weighing yourself daily, take the average over a week as your "actual number."