The first thing you are doing wrong is trying to lose weight for a one day event, not as a lasting life style change.  After the wedding, do you plan to go back to the life style that has caused your weight problem? 

Weddings can be stressful even if they are happy events.  You may want to wait until after the wedding to take on the challenge of reshaping your lifestyle.  By that time, you will also have a supportive partner to share this with you.  Remember, your fiancé fell in love with you and asked to spend the rest of his life with you just as you are now. Whatever your weight is now, you will make a beautiful bride.  Start to clean up your diet by taking junk foods out and don’t replace them.  Replace your current foods with healthier alternatives and cut down on your serving sizes.  That’s enough to do for now.  Once the wedding and honeymoon are over, you will be able to focus on reshaping your lifestyle. Also start to journal your food intake and consider using a site like Calorieking.com or Fitday.com to track your food intake. The number one problem with losing weight is that we underestimate how much food we eat. Track it for a week and see.

As a professional in the fitness field for many years, I see temporary lifestyle changes both in diet and in exercise to deal with a long term problem.  Believe me, it does not work!  The last thing you want to do is follow a crash diet and really mess up your metabolism. I recommend losing the weight slowly and correctly and with the help of professionals in the fitness field. A safe total weight loss per week is 1 pound. There are 3,500 calories in a pound, so in order to lose 1 pound in a week, you need to create a 500 calorie deficit per day. Over the course of a week, this equals 3,500 calories or 1 pound.

One good way to hit this 500 calorie number every day is to create a 250 calorie deficit through your diet and another 250 calorie deficit through cardio exercise or weight training. Remember, to fuel your body with high quality foods and keep yourself fueled throughout the day. Don’t limit your food intake too severely as that tends to cause your body to go into starvation mode and hold onto your fat reserves.  This may be what you are doing since you say you are not losing any weight. I recommend eating at least 1,500 calories per day and make sure you're eating whole, unprocessed and nutritious food.