My wedding dress doesn't fit

<3 Karessa
I found my dress it fit perfect on me that was a months a go. Our wedding is in 12 days from now. I just tried on my dress it's a very tight fit. Omg I'm so upset I been so good on what I'm eating and how much. I put on 10lbs in just 2weeks?? My af supposed to come tomorrow if I'm not pregnant. Any ideas how to lose weight fast???