This is because the band of the bra is too big, you need a bra with a smaller back size i.e. if you wear a 36 try a 34.
The under wire is digging into the side of your breast.
Your cup is too small, the under wire should encase your breast and not dig into it.You need a bra with a bigger cup size.
You have indents in your shoulder where the straps have dug in.
This is caused by the back of the bra being too big and the cup being too small, making you pull the straps up too tight for support.You need a bra with a smaller back and a bigger cup size.
Your Breasts falling out of the bottom of the under wire.
The back of the bra is too big and the cup too small.You need a bra which is smaller in the back and bigger in the cup.
If you get a bumpy silhouette under your clothes.
Your cup size is too small causing your breasts to overspill. You need to increase your cup size until you get a smooth silhouette.