see, I'd been told both times before that after 16 weeks you should never lie on your back, although with both my girls I woke up from time to time on my back and was just fine. I did have tingling in my feet once, but I think I was about 8 months. I usually try to get comfortable other ways first. I have found that I can't sleep on my side when pregnant unless I have a pillow under my waist to support my spine. I have a foot difference (when not pregnant) between my waist and hips, so when you have a pregnant belly pulling down on an area with no support it just causes pain. If I have a pillow under my waist/side, 2-3 between my knees and a body pillow the length of my back I'm usually rather comfortable. Have I mentioned how much my husband likes pregnancy sleeping...lol I got 5 more pillows last week so he could have one too. Of course, my dd decided she liked the new buckwheat pillow better than hers, and traded me all of hers for it too. I've also tried memory foam and feather pillows with my new stash. I like the down the best for my head, but the memory foam is awesome for propping up on my back at night. It doesn't give you any of those uncomfortable uneven lumps in your back that make you wake up with back pain.
Hope y'all are able to find some comfort at night. Last night was aweful for me, but I slept great today...almost all day