helllllp

What's the deadline for having your dress altered? You don't need to hit your goal the day before your wedding; you need to hit your goal before your last chance to have your dress altered.

Here's the thing -- you have no control over where the weight is going to come off, which is why it's a very good idea to make sure you hit your goal in plenty of time so they can tailor the dress. The last thing you want to have happen is for all of it to come off your waist, for example, and then find out that they can't take in that much from the waist of your dress. (You may lose it all from your face and your calves, or wherever. There's literally no way to tell, unless you have liposuction).

You have about 15 weeks to lose 21 pounds, which should be very do-able. I'd see what MFP gives you to lose 1.5 pounds per week, and make sure you're calculating everything as accurately as possible (that means using a food scale). If you can safely go up to 2 pounds per week, do that now. Weight loss tends to slow down as you get closer to your goal, so you may not be able to continue to lose 1.5 pounds per week the whole time. Starting a little more quickly will give you some leeway at the end.