I went shopping with my mom for a prom dress today and although a lot of the dresses were quite flattering around my flabby stomach I was disappointed that my usual size didn't fit me

I don't want to look like a stuffed sausage but i also don't want to go a size bigger. I'm considering restricting for the next week until prom but I'm not sure if I'll be able to stop..is there a healthy way to get off the extra belly fat? I'm not allowed to weigh myself so that wont matter...? what to do??