My boobs sag and are empty since I lost weight. What are my options? (Photo)

A breast lift is one good option to get rid of the sagging and make your breasts tighter and perkier. It is best to consult with a board-certified plastic surgeon for an in-person examination. 

Based on your photos and your own description it appears that a mastopexy augmentation would be the best solution.  An in person consultation where actual measurements can be taken would aid in the decision making process.
best wishes