Chances are that you bought your bra on your own and are just not sure whether it fits the way it’s supposed to. Even if you did receive a fitting when you originally purchased it, weight changes, pregnancy, and breastfeeding may have since changed your size and shape, creating new doubts in your mind. Not to worry. With the help of a mirror, there are some easy ways you can determine on your own whether you’re wearing the wrong size. The key areas to look at are the principal components of every bra: the band, the cups, and the straps.
Before we begin, remember that when evaluating the fit of a new bra, make sure to try it on using the loosest hook. Over the bra’s lifetime, washing and wearing will cause it to stretch, so you’ll want to be able to use the tighter hook settings in the future.Source