I was going to say Ebay. Last summer I bought a couple of elastic waisted skirts from Katies - the long tiered ones, and they have been super. I just chuck one of those on and a preggie top and I'm really comfy.
I'll also admit to wearing lots of exercise pants and long T's - but to be honest we have only had a few hot days here so far, so I'm still in long sleeves alot of the time!