Rachel - Should you be worried isn't the question - because obviously you are! At your age, the possibility of cancer is remote. But kudos to you for paying attention to your breasts, and noticing differences/changes. My advice: make an appointment with your doctor, so he/she can do an exam and explain to you what's going on. I'd think it has something to do with puberty and growing breasts... but meeting with a doctor should go a long way towards setting your mind at ease. Take care, Rachel - PJH