Sorry! Typo!
I meant to say "That will contribute to the weight gain you're seeing."
You're metabolism has probably just slowed because you've been depriving your body. Like any eating disorder, once you start eating normally again, your body will store what it gets, just in case it won't get food again. The trick is to eat small but frequently, stay active, and your metabolism will go back to normal.
Chewing and spitting contributes to water retention as well, so that will add to the weight gain you're eating. Don't quote me on this part because I don't know for sure, but I've read that chewing and spitting too often can cause unhealthy insulin levels, which is another hormone that slows weight loss. Like I said, I don't know that part for sure, but c&s isn't healthy regardless.
Your best action plan before your big night would be to get on your feet and get moving! Eat small, whole food snacks and keep hydrated. Don't expect a miracle overnight. Keep at it and you will be fit and gorgeous in time for the formal!