Take a step back and relax, and remember: pretty much all brides look great on their wedding day - happiness looks good on everyone :-)
Don't forget, on the actual day of, you'll have your hair done up, makeup on, and it'll like way different (in a good way) to how it looks in the store.
There's lots of pressure on "the dress" but as long as you know you like it, you'll be fine. Once your future husband looks at you and tells you how great you look, all that anxiety will melt away!!