The key to pulling off casual bottoms, especially something like your workout leggings, is mixing it with super luxurious tops, bags and shoes to polish the look.
I've been wearing a lot of my old Stella McCartney T-shirt dresses as tops over my bottoms. They are long enough to cover the areas I really don't love right now and I get complimented on them all the time. Because Stella makes them, they hang just right.
Another absolute key is my cardigans. I've been wearing the above two often (one I bought at Madison in Pacific Palisades on sale and it is Missoni and the other is Joie from Intermix). They are beautiful and a nod to spring colors. They keep me warm, comfortable and covered. I wear long silk and super soft cotton shells under them to keep the look polished as you can be while being 9.5 months pregnant.
The final touch is to wear nice shoes. I've been alternating between by Rag and Bone boots and a pair of Grey Nubuck Stella McCartney wedge booties I adore. They give my look just enough edge and give me a little height to slim out my look. If you absolutely can't bother with a heel right now (I completely understand) I wear Homer's brogues I bought in Spain or a pair of Lanvin flats. Again, adding super nice accessories to your look of basics will help elevate it above the leggings, sweater and running shoes vibe so many Angelenos rock outside the home.
Hope this helps you feel a little more beautiful!