I totally had the same problem... I'm a size 16 or 18 with boobs to match, so trying on wedding dresses was hell. We got married at the court house but I still wanted a decent dress, you know? My mom and I went to David's Bridal when they had one of their big sales and struck out with the wedding dresses, but I found a less traditional old-fashioned number in the prom dress section that was on sale for $50. It was my style, fit really well and didn't need to be altered size-wise. I know most people want a "real" wedding dress, but you can totally find some stuff in the formal section that looks just like the average traditional white wedding dress for less $$ and could probably be altered a little bit to fit your style for not very much more.
Please ignore my toes sticking out at the bottom... darn shoes hurt