Hi and congrats!
I would start out small. Make small goals liek drinking 8 glasses of water a day, or walking 1 mile everyday. This way u can work up to bigger goals like losing 2lbs a week (which is what is normal and healthy).
Watch your calories and stick to the calorie range that Spakr gave you. Also start excersising. If this is new start small, again maybe just walking 30 minutes a day is better than just sitting and not doing anything. Eventually u will start doing more!
Lastly you will look beautiful no matter what on your wedding day so don't worry about what u will look in pictures. Everyone is happy and radiant on that day and it will show no matter what size you are!