Saggy breast

Summer
My son is only 3 weeks old and loves to eat he eats almost every hour or every other hour. Im only 20 and i feel like my boobs will b to my knees before hes even 1. I love breast feeding him because it's healthy but every time i look at my boobs or body i feel a little discourage because im not even old and my boobs are sagging already. I keep thinking once hes 3 months and im working ill give him formula and hope my boobs go back to normal well at least wont sag to bad... Idk what to do ...