I have been losing weight for my wedding like most of us

but I am not sure when to get the alterations done? I want to keep losing weight as close to the wedding as possible but I am not sure when to stop and keep where I am so I can get the Alterations done, and keep my body the same so I dont have any complications with my dress the day of the wedding. How far in advance do I have to get this done in order to have my dress back in time? Any help is greatly appreciated!