I feel exactly the same way! I have been really, really good, haven't gone over 1300 calories, I've worked out at least 4 days every week (really working out, I'm on week 5 of Couch to 5k, and after that I do 45 minutes to an hour of weight lifting) and my weight is exactly the same as where it was last week on weigh-in day.

Granted, I wasn't supposed to weigh in until tomorrow, but I thought that even though I started my period yesterday, I would see SOME loss.
Oh well, I'm definitely eating more healthily, even if I'm not losing weight, right? So let's just hang in there, girl!