Bky!
Though you can see dramatic weight loss on SBD, it's best used as a lifelong change of eating patterns.
It's great to have goals that help you stay motivated, like your sister's wedding, but trying to lose weight quickly isn't a good thing for your health or your metabolism--one of my friends kept up a routine of eating whatever she wanted and then doing fad diets to lose quickly and ended up with a metabolism that literally burned no more than 300 cals a day!
It's not a good idea in the longterm, so I hope you're planning on making a change to healthy eating (that is, if you aren't already eating healthy!
) that lasts even after your sister's wedding, Bky!
Are you exercising? You'll find that as you lose fat, if you increase your muscle, you'll be smaller, even if you don't officially lose a pound on the scale. A pound of muscle is smaller than a pound of fat (you can see a photo stickied in the Exercise forum here at 3FC) and so you can fit into smaller clothes sizes even at the same weight. You might consider adding strength training and cardio to your routine if you don't do them already. It'll really help you with your goal of fitting into that dress. I'm sure you'll look beautiful!