Its best to sleep on your left even when not pregers because of the organs and what not. But as long as youre comfy you can sleep anywau you want. You just shouldnt sleep on your back but if you find yourself on your back dont freak out and just turn over its not like out of billions of pregmancies women didnt sleep on their back it happens just roll over if you catch yourself doing it
I just asked my doctor about this he said its ok to sleep on both sides but not really good or even comfty to sleep on your back. I'm 35 weeks btw