Is a breast fat graft helpful for sagging breasts after childbirth?

Before marriage, I had a moderate breast volume, but after giving birth to my second child and possibly due to improper breastfeeding methods, my breasts have sagged and lost all their volume. Because I am self-conscious about my sagging breasts, I am worried about what others think, so I avoid going to jjimjilbangs or public baths... ㅠㅠ

Would breast fat grafting or plastic surgery help in this case?