Like twiceblessed mentioned, exercise will help tone you up which, in turn, will loosen those clothes (that doesn't sound right, but I hope you know what I mean!). Also, some of that may be water weight, which I don't think you notice as much. I know in the past, I used to gain weight the first week or two of a diet. Without fail, I'd be up 2-3 lbs and then it would start coming off. Everybody's body just works differently.
Regardless, I hope that you stick with it. Even if you're not seeing the results just yet, that's 15 less pounds that you're carrying around on your body. That's a great accomplishment! If you don't believe me, go to the food store and lug a 15 lb turkey around the store for a while.