I changed my size just once and tried to make do with it coz i didnt want to buy so many bras only to use them for a few months , and then switched to maternity bra probably in third trimester.
I only bought 5 nursing bras from Lovemere to go about, and used bra extenders for my old bras. bra extenders will be your best friend during pregnancy. https://s.shopee.sg/2Axbbx6qJB
I only started to feel that my bras became suffocating at my 5th month of preg.. i bought new ones after that!