I have very saggy, empty boobs too. I have lots of excess stretched skin with LOADS of stretchmarks. I measure about a 30C, but look tiny because there is nothing but skin. I went from a B cup to a G cup with my first pregnancy, had 2 more pregnancies and then lost lots of weight. My boobs are now a mess.
My surgeon is giving me a full uplift and implants. Because my skin stretched so much, it is now really thin, so there is a higher risk of rippling from the implants. Because of this he advised upgrading to Natrelle implants. I cant wait to have boobs back where they belong!