Don't worry! You're normally a size 12 / 14, maybe their dresses run a bit small there. I've had that happen to me, where I'm at size 7 at 99% of stores, then I go into another store and have to get a size 9 because their clothing runs small. I assume the wedding would be late June or early July, that gives you quite a bit of time to drop at least 10 more lbs, if not more. Remember, it's not the size or the weight, it's how you carry it and I'm positive you'll look beautiful no matter.