are you weighing @ the same time every day? (I actually prefer weighing once or twice a week, 1st thing in the a.m.)
Also be sure to place your scale in same spot every time you weigh. My digital scale shows a 5-8 lb fluctuation, depending where I put it in the bathroom!
If your scale's unreliable, find a new one... I hear weight watchers has a good one.
If you're losing a pant size even though the scale doesn't jive, it may be the exercise... my butt started shrinking right away when I started the treadmill. You are making excellent progress, enjoy and keep kickin' butt!!