Let’s look at the bra you have been wearing
Do you fill the cup and is it smooth?
Or is the cup slightly small, are you spilling over the top?
If so, do you need to go up one cup Size?
If it’s a C then a D might be better.
Or is your cup roomy inside?
Do you have any gaps or wrinkles in the cup or is the top cup empty?
If so… you need to reduce the cup.
If you are wearing a F then a E might be better.