Nature says otherwise. If, without being unkind, a flat chest woman can breastfeed then nature created breasts for what reason?
Now I understand that if the OP is physically struggling then she has the option for breast reduction. But as a long time poster who is familiar with the lifestyle you'll know that, for the most part, it's a fat related issue. If they lose fat their breasts will get smaller. It's the only reason why cup sizes have grown - cos women (and men of course) have gotten fatter.