Oh wowee!!! Congrats Day Vies! I've missed your fab style and this is the best news--I'm so glad you're back and I can't wait to see your maternity style. You are positively glowing and I am so excited that you're having a little Day Vies to follow in your fab fashion footsteps!
I have some links to my maternity outfits in this post:
I was lucky that I was able to stretch my pre-pregnancy wardrobe and buy very few maternity clothes, because I knew it was going to be the last one. I bought maternity black skinny pants from H&M, burgundy skinny cords and a mustard tunic top from Pea In the Pod, and maternity Always skinny jeans and a tank from Gap. I could be mistaken, but I think that was about it that was specifically maternity. The rest of the things I wore were either stuff I already had, or stretchy non-maternity clothes I bought while pregnant. Bonus is that I can still wear that stuff now, it just is a relaxed fit (which happens to be in).
You can still wear your old tops even if they are short, if you layer over a maternity tank, or hike up your skirts and make them high-waisted. I bought several of those Vince Camuto midi tube skirts and Target Merona ponte pencil skirts and I was able to wear them even up to delivery!
Here I am at 38-40 weeks and ready to pop, yet none of it was maternity wear!
Same with my stretchy wrap and faux wrap dresses--still wore them in 3rd trimester and they just became a little shorter, but still wearable:
And I loved adding capri leggings under my regular dresses to make them into tunics when they became short due to the big belly:
You can also wear your old button down shirts, open over a maternity tank.
I also used belts a lot to define my "waist" and just belted above the bump (which ended up being right below my bust toward the end of pregnancy).
I wouldn't worry too much about stretching out knitwear. I actually have been wearing most of my clothes post-partum as well and haven't found that anything was "ruined" by my wearing it during pregnancy. The Target leopard skirt and the H&M fur collar burgundy cardigan are a little loose now (maybe because I had bought them a size up), and the Gap dolman sweaters I haven't felt like wearing, but everything else has held up well. I am not a small capsule dresser though, so I don't wear my clothes super hard. I went the "adapt a large wardrobe creatively" vs. the "buy a minimalist maternity wardrobe" route. I think both approaches are great though--others who are more minimalist would probably do well with jazzing up the basics with lots of different accessories to change things up. (Purses and jewelry and shoes are great things to shop for during pregnancy since those don't typically change size!)
Hope this helps, and congrats! Can't wait to see what you do with your wardrobe during this happy and exciting time!