C.V.
You're not screwed. :-) This is a pretty easy fix.
Put some warm (not hot) water in the sink. Add about 1/2 cup of hair conditioner or baby shampoo. Mix it in. Put your dress in to soak for 30 minutes. Wring it out and get as much of the liquid out as possible. Then gently stretch the fabric back to shape. Hang it up or lay it flat to dry. Don't shrink it again when you wash it. :-)
Here are some detailed instructions. http://www.onegoodthingbyjillee.com/2014/07/unshrink-clot...