You shouldn't after a certain week but I can't remember which week. Just go by what your body is telling you. Like I can't sleep on my back right now at 16 weeks because I get nauseous and a headache. But I do wake up on my back sometimes which is okay, you can't help how you move while sleeping. I also can't sleep in my right side because I get super nauseous. So yeah, only sleeping on my left side is getting super annoying.
My mom went ahead and booked a big family photo shoot for Feb. I'm kind of mad because a) I don't want to be huge and pregnant in a photo shoot (I'll be 7 mths) and b) why can't she just wait the 2 mths and have the baby be born and in the photo shoot with us?