My left breast big sagg and the aerole big my right breast small don't sagg and the aerole small why my breast different sizes?

Breasts aren't twins: Breasts are usually cousins, sometimes sisters, rarely twins and sometimes they don't even know each other! almost every woman has non-identical breasts. Differences as you are describing are rare but do occur. I have had to, on occasion, perform a reduction on one breast and an augmentation on the other. Your plastic surgeon should be able to improve your particular asymmetry. Good luck!