Don't get upset about the weight! I had been concerned about it, as well. I finally got to the point that I was cranky eating yougart and fruit all day. The stress, antcipation, and excitement will bring a few pounds off in the last few weeks anyway.
Also a note. I normally wear between a 6 and a 8. My dress from David's Bridal was a 10. The have a tendency to run small, not true to size. You're better off having lots of extra space for any alterations you need or want, too. I totally changed the neckline on my dress. The seamstress mentioned how grateful she was that the dress was big and that she had room to play with it.
One of the best things you can do for yourself is exercise... and I mean that in a totally general snese of "best thing you can do for yourself." Walking is an easy and pleasurable way to get your heartrate up. Sart taking strolls with DFi or the dog in the evening. It will make you relax that much more, too. Just remember not to sabotage yourself and eat sensibly. Eating in can save you huge amounts of fat, salt, and calories. They estimate that when you eat out, you are eating 40% more in portion size, salt, fat, and Caloric intake than you would by eating in. If you must eat out, grab a salad or lighter meal option.
Remember, you fiance already thinks you are the most beautiful woman in the world. When he sees you on your wedding day, the dress, veil, hair and make-up are just a wash. He's looking at you, his angel, as he takes those vows and none of the material frills.