...your bra keeps riding up in the back.
...you have breast tissue spilling over the top of your bra and have uncomfortable bulges under your arms.

...your bra straps slide and keep falling down.
...your breasts droop, bounce when you walk and play sports, and your blouses pucker and buttons pull.
...your bra straps dig in your shoulders and you tend to slouch, rather than stand up straight. 
...your underwires gouge, dig or poke your breasts and you have deep, painful dents under your breasts.