My breasts grew two sizes in a month..?

I'm 17 and was pretty flat chested and all of the sudden I woke up one morning and it seems like they grew A LOT bigger. Iv'e had my period since I was 10. What do you think some causes are for this sudden growth? I'm not on any pills or anything either.I am also very happy that I finally filled in! lolMy breasts grew two sizes in a month..?
So will a lot of boys and some girls be as well.
Everyones hormones function differently. Because everyone is different.
But once it starts to kick in it usually snowballs. Hence the term "overnight"
you're a late bloomer
Have you been having sex or getting more emotionally attached to a particular love interest? If so then your hormones would have kicked into a higher gear, causing your breasts to enlargen.