Underwire bra leaving red marks under breast, what sthe problem?

i am so sick and tired of trying on bras and returning them to the store i must of returned 10 in 2-3 months. i dont know what i am doing wrong i have measureed and meausred and cant diagnoise my problem. i am a 40DD or a 42DD or in some 42D if i am correct i am so sick of this in 1 style i have tried a 40D, 40DD, 42DD in all three i have experienced red marks, in the 42 i experience a bit of ride up, in 40 i experience red marks whole way around. in the DD cup i find my slef having to constantly put my self back into the cup or diging like feeling on sides. and sorta with the D cup but not as bad also with the D cup a bit of buldge hanging out (which i know that means its too small of cup) but with a DD i find it with a bit of extra fabric like(which i know is too big) i feel that i am inbetween sizes on bands. but i am bout to give up up with the cup, i do not know what to do.