I always weigh myself in the morning right after I pee... it's the lowest number of the day and I like that!
As far as your weight being bouncy... it could be salt in take, carb in take, TOM, Traveling, Muscle mass (when your muscles are sore from working out, that means that they are swollen... which means water retention). Lot's of factors could be causing it.
I say take a deep breath give it a little time. If it's still doing it, then maybe that's how your body deals with loosing the weight.
Hope this helps.