What Causes Breasts To Shrink?

hi i think my breasts may be shinking. they feel smaller and seem less full my partner says he thinks they look smaller too. am a 28 year old woman i eat pretty well i don't diet or exercise and am natural slim. 6 months ago i stopped taking the contraceptive pill after 12 years of being on it but other then that nothing else has changed. i remember my mother telling me that her breasts disappeared after she had kids but i haven't had any children.

do you know what might be causing my bust to shrink?