well if u don't own a sport bra maybe u don't have enough boobs for one orrrrr you're not old enough to be taught that yet lol js
I hate when your all dressed up showing alot of cleavage (which is me all the time lol) then you have to run for a bus or something and your boobs nearly fall out of your top :-( the stress of the big boobed girls :-(
Maybe.... Cover up? Seems like a pretty good solution. If you're wanting to show boob then you shouldnt be mad when they pop out.