When to buy nursing bra

I’m 37 weeks. So I’ve bought a couple of night time nursing bras already to use during labor and to have right after birth. But I am in need of a really good nursing bra and am planning on going to Nordstrom to get fitted so they can find the most supportive bra for me. My boobs are so big (F now) so I need great support. Is it too early to get fitted now, or should I wait until a couple of weeks after the birth when milk production has been regulated?