I find that I can get really demotivated by the scale and flucuations...especially when you first start out and lose water weight, salt, etc. I try twice a week - but previously I was very successful also trying on clothes to see how they fit. Often, the scale would not budge too much, but I could tell that I lost inches by the way my clothes fit. And I do not go near the scale around my peroid - lol.
I hear you about can't believe the number, in my case I took pictures tonight and I am still shocked and can't sleep