My breasts have shrunk for no reason. I have been on the birth control pill for 4 years, and they grew when I first went on it but for the past year they have gone down a cup size. I have also been lifting weights for that year, but I do not look any different (in fact I weigh more) and the ONLY thing changed was my breast size. I'm only 23 and I am concerned about a hormonal problem because there is no natural reason for this. I just hope they don't get smaller. Please do not suggest breast implants, I don't want them.