Please help! Pregnancy/nursing bras!

Why are all bras rated only for tiny women!? 😒 my bras are getting too tight and I will be breast feeding so I figure I better buy nursing bras but I can’t find like any that provide enough support or underwire for us plus size women. I was about 42DD before pregnancy and I’m only 13 weeks and already uncomfortable.

Also do you order your prepregnancy size or how are you supposed to know what size? I like ordering off amazon. I don’t live near any good stores.