Wow...you do have a dilema here. How much of a difference are you planning to attain with this surgery? What size are you now, and what has you doctor said you will be by November...I assume this is still you wedding date.
Why did you schedule your surgery at this time? Your probably not going to be able to order by what your doctor projected. A dress is easier to take in than let out. Which is probably an option you are going to have to rely on. Safer to order what fits you now and have it altered.