Oh, my aching sciatica! That's how my third trimester started. If it hurts, ask your OB to refer you to a physical therapist! The single most helpful exercise for me was the modified wall sit. I press (flatten, neutral spine) my back into the wall with my thighs at about 30 degrees from the wall. Repeat as needed. The sciatica went away when I followed the right set of exercises. One such set (I'm only using the wall slide) is here.
Each day I say that I've never felt so stretched ... and then the next day comes. I think the shea and cocoa butter lotions I use do help, but that could be in my head (still helps!). My first trimester visitors of thirst and fatigue are back. This time when I drink water, I can feel my belly expand. And since there's tremendous growth, I assume that explains the desire to nap.
It's cruel irony, but my sleep patterns have already changed for the worse. I now measure how well I slept by the length of the times I stayed asleep. It's usually 90 minutes, but sometimes half that. One night I got two batches of three hours each (and then a sound two hours on the couch), and that felt heavenly!
Favorite food: grapes! and still eating half a grapefruit for breakfast as long as the citrus season holds out. (Still can't handle fat and salt.)
Almost done! Keep exercising, and get as much sleep as you can (both to reduce pain).
Total weight gain: up 16 pounds.