I used to wear either a 32c or 34b depending on the bra, i had 400cc same as you, they say go up a back size but because i wore both 32 abd 34 i was unsure if to get a 34 or a 36… anyway i went for 36dd an it was a really good fit for me you will find the first couple of weeks you are swollen all over. I got a couple in 34e an they fit well after the bloat went down xx