How do you buy clothes for pregnancy?

FTM about 17 weeks, but I’d really like to take advantage of the upcoming Black Friday sales at the end of November to buy any clothes for the remainder of my pregnancy. I’m showing just a little, but right on the edge of being uncomfortable in my jeans. I’m hoping to buy things that will get me through the winter and at least some of spring. My shirts are already too tight.

How can I know what sizes to buy since I can’t predict how big I’ll be at any point? Any advice much appreciated!

Signed, a mama to be who would give anything to feel good in her body again by wearing some real clothes