Wedding Dress arriving late!

My wedding is October 1, 2016. Last night, I took a few people to go wedding dress shopping for the 2nd time at David's Bridal. I had no high hopes for finding a dress at David's Bridal since I never heard any good reviews about it. Color me surprised, when the last dress I tried on was perfect. I had my "wedding dress moment" and cried. So, I said yes to the dress. Upon ordering it & paying for it (final sale), I realized that my consultant did not order my dress in petite. (I'm 4'11, I NEED a petite). So, I called this morning to change my order for a Petite size, but now my dress won't be arriving till August 09 (at the latest!). That gives me less than 2 months with the dress without any alterations. David's Bridal assured me that though it's cutting it close, I would be able to have a fitting and alterations the week my dress comes in and have it before my wedding. I NEED PEACE OF MIND. Can someone give me any advice or words of encouragement that I'll have a wedding dress?!