4 fundamentals of fit
Straps shouldn’t slip or dig. And if they feel like the main source of support, you may need a smaller band size. Try adjustable straps for a more custom fit.
Make sure the underwire sits flat against the body. If it doesn’t, go up a cup size.
Your breast should be fully contained in the cup, but make sure the bra doesn’t pucker or wrinkle. Spilling out of the top or side indicates the cup size is too small.
On the middle hook, ensure the band is snug and lies even. If the band rides up, it’s too loose and/or the straps need adjustment. Chafing can occur if the fit is too loose.