How to enchance breast without surgery?

At age 13 I was diagnosed with narcolepsy and gained over a hundred pounds. Now I have lost all that weight but I hate the way my breast look. They are flat at the top and full at the bottom and they sag. I am only 20 and don’t want to have surgery. Is there anyway I could lift them up besides wearing better bras and surgery? And how do I get them to stay in a bathing suit top?