I am sure a seamstress will be able to make it fit. And if you happen too loose too much until the wedding, just wear a padded bra.
And you still have plenty of time to loose an inch without going to the extremes. Maybe just focusing on loosing some water weight could help? Cut back on the sodium and up the walks and water. You can do this!
And if all fails I recommend trying some kind of shapewear. (if you can fit that under your dress that is.) I have a few shirts I use because the back band on my bra and the bra straps creates bulges on my back. Personally I think the shirts are uncomfortable, but when I _need_ to look good for a few hours I will just squeeze in and grin and bear it. Better than having boobs both front and back ;)