Okay not a baby question, a nursing bra question.

For ladies who have had a baby before and have worn nursing bras, did you have to buy the size you are now or should I go up 1 cup size because once the milk supply is fully in my breasts will be fuller? I'm currently a 46D I was measured just recently to make sure. But no Maternity stores carry a 46D so I have to order online. But wondering if I should go for a 46DD? Because my boobs are feeling fuller now that I'm 9 days away from my due date. Thanks in advance!