Why am I only a 10B when im 13 ?

your absolutly normal. most girls your age are a-c. dw, they’ll grow. also depends on your height

because your only 13 what you don’t realise is that breasts don’t just magically appear when you turn 13 and you have only just BEGUN to go through puberty breasts take YEARS to develop and they will reach there full size by the time your around 18-21 there is NOTHING you can do to make them bigger no pills, creams, exercise, foods and other crap works eating food and getting fatter ALL over your body will make them bigger, but certain foods and drinks, ect do not work all you can do is be patient and WAIT for them to grow they will be done growing when your done going through puberty and you’ve barely even started it also you and your friends develop at different rates so what’s normal for them is NOT normal for you in the meantime if your that desperate you can use padded and push up bras but at around 13 the size of your boobs should be the least of your problems because they’ve barely started growing