How pregnant are you? Have you bought maternity jeans/trousers yet? I would consider this before choosing your boots. I bought some lovely ankle boots this year, but have hardly worn them because I can't find maternity jeans that are skinny all the way to the ankle. If you get another long pair make sure they have a zip so you can get them on and off towards the end.
I'm doing a massive clear out of shoes for winter as so many of them are "done". Got a good pair of long black flat boots which are great with leggings and skirts, got red flat pumps, got black elegant heels, brown suede wedge shoes. And a pair of clarks black Chelsea boots (what I don't like). The rest are being binned. So what casual everyday boots, can wear with leggings or jeans, do other folk wear? I'm no trend setter but I dress smart casual ESP when pregnant so I look good most of the time.