Realistically, most people don't lose more than a pound or two in the first two weeks. Some people don't lose any weight for the first 2-3 weeks. (The results on the Biggest Loser are NOT typical for people in real life.)
But you are doing great! You are doing the right things for long-term health.
It's not you. It's the dress. It just fits differently than your usual clothes. Don't worry about it. Keep concentrating on you good habits, and you WILL make progress.