How To Increase Breast Size?

hi im a slim 17 year old girl about 100-105 lbs. i used to do karate and realised that the sport made my breasts firm and appeared bigger. to when i stopped, i realized that they started to droop and look smaller. i wanted to get back the initial appearance so i worked my chest area really intensely such as pushing against the wall, and at the same time i did swimming. after that period, i realized that my breasts size reduced. im getting worried and i wanted to know if i would ever get back the breast fat that i lost? please help