I was a 32A pre (1st) pregnancy by the time I had Summer I was a 34C and after my milk came in I was a 34DD.
When I stopped BFing I went down to a 34C where I have remained until a few weeks ago and they have started growing again
mine didn't 'sag' but I always wore a bra even to bed, that said they definately aren't as perky as they used to be but I think that has to do with age too! they can't be perky forever right?!?!