As I've mentioned in several threads, for about a month I wasn't losing at all. I then started using Fitday and realized that my calorie count was down around 1000 a day. I upped my calories (fat, mostly) and started losing again.

At your weight, you should be aiming for about 1600 calories a day. Under no circumstances go under 1200 regularly. (Once in a while won't kill you, but you don't want it to become a habit.)