Hiya! Congrats on your weight loss so far!!
You really do need to get out there, most dresses take about 16 weeks to come in but they can rush dresses through - some bridal houses charge a premium for this though.. You may be able to buy a sample dress though and just get it cleaned, would save you a lot of time.. (most bridal shops put there's in the washing machine inside a duvet cover, 30 degree wash, gentle spin cycle, comes out perfectly! Saw that on a thread on a well known wedding forum and everyones dresses have come out perfect so far!)
With respect to the sizes, get a dress which fits.. I ordered a dress the same size as the shop sample which, when I was half a stone lighter, fitted.. I then put on another half a stone - so I was a stone heavier than when the sample fitted when my dress arrived.. Couple this with the fact that the sample had stretched through so many people trying it on and all of a sudden my dress didn't fit by 4-5 inches... The pressure I'm now under trying to lose weight to get in my dress is unreal but at least I've got the time to do it, it's so so much easier to make a dress fit a smaller bride than it is to make a bride fit a smaller dress!!!!
And the earlier post about the sizing is spot on too - wedding dress sizes are varied from bridal house to bridal house, the majority of the time though a size 12 bride needs a size 16 dress... So go for a size wihch fits, ignore the number on the label.. People see the dress babe, not the number inside it!!
Good luck dress shoping, it's wonderful fun!! Try on loads of different styles, I've known so many people who wanted one type of dress and bought something completely different (me included!!) - things look so different on the hanger compared to being on! I wanted something ivory, with straps, plain, simple and elegant.. I've now got gold, lacey, strapless, beads on the bodice and the complete opposite of what I thought I wanted - but I love it!!
Have fun, let us know how you get on!!