I use yoga pants or shorts, I just buy a bigger pair for pregnancy.
I live in my fold over yoga pants!!!
I have found a few nice pair at Costco and sams club. Just get a size bigger and they fit better. This can give you the fit you are looking for but some room.
I got a pair of yoga pants from maternity motherhood. They have extra room in the belly and can be worn folded or over the belly. And they stay up!
Definetly yoga pants because it won't squeeze your belly & you can use them like maternity pants. I went to target last week & they had a sale both short & long yoga pants. They are so comfortable that I don't want to wear anything else plus you can dress them up or down if you like.