Some dresses take a year to order, but mostly they come in anywhere between 6-9 months and some even earlier. If I were you, I'd probably start now. The bridal shop will let you know how long each gown takes to come in after being ordered.
You can definitely start to try them on now. Even with weight loss, unless there's an extreme amount, you'll lose a little from each part of you, so you may drop a dress size, but your overall proportions and body shape will likely be similar (in other words, what looks good on you now will also look good on you dropped a size!). You probably want to order it at least 9 months in advance so now is ideal to start looking! Also, once you know the diress, the boutique could call and find the 'cut date' (designers cut just a few times a year, not as they receive orders...), so if you lose significant weight before the cut date, they can order you a smaller size.
I would start now as well
I would start now - don't worry about size unless you plan on losing more than like 50 lbs. It can always be taken in!
