Congrats!! When I got married I lost 50lbs in 6 months. Bought the dress on the heavy end. Bride shops are used to all sizes! I had it taken in significantly before the wedding. I was similar to your size.
You can wait a few months at least for the dress shopping. If you stay on track from today you can lose the better part of 10lbs per month and in 3 months that is significant! One day at a time, each day on track. If you fall a bit pick yourself up the next day and carry on.
And come here everyday. I find I have to check in everyday at least just to read posts and stay motivated