Weddingbee boards

So I have my first dress fitting tonight at David's Bridal. I have my wedding dress at home with me b/c it was a discontinued dress and I bought the last one so I got to take it home with me. I bought the dress smaller than I was b/c I was planning on losing weight. So, the whole 5 months I've had the dress it's never fit. I've lost 32 lbs since getting engaged, but the dress still doesn't fit! Its about 2 inches from zipping up all the way. My wedding is in 43 days and I'm afraid the alterations person is going to want to put in a corset back or let it out an inch. I really don't want to do that. I'm just really nervous about tonight and starting to get stressed that I won't be able to fit in my dress in time. I have 4 weeks until my bridals also, which adds to the stress. Any advice?

I really don't think shapewear would help....its not fitting at the top of my back. My mom said I might just have a wide rib cage. I just really don't want to let it out. It is loose in the stomach and hips.