You should go and get yourself measured to see if you are even buying the right size. And try finding the kind of bra that is perfect for your breast shape. Like personally, demi-fit bras work the best for me. But even for someone else that wears my bra size, could have a different kind of bra that fits them better. It sounds weird i know. You should also get new bras about once a year. I hope this helped. :)

Remeasure yourself!!

This happened to me and i got re-sized and found out i was a bigger cup size than what i was buying! also, the fit of your bra might not be right for your boob shape (it sounds weird, i mean why can't we wear whatever bra we want? but yeah sometimes the fit has an impact as your boobs change shape).

Do you hand or machine wash them. Hand washing and air drying is the best. If they are a year old or older, it is time to replace them.

This happens to me too!!