How to lay

Abigail • Pregnant with #2 & twins this time!
I'm now 17 weeks pregnant as of today with our twins. I heard you're suppose to stop laying on your back by about 14 weeks. Well, I always fall asleep on my side with my body pillow but I almost always wake up laying on my back and I'm not sure how long each time I have been laying that way. I can't really help that I flip on my back. Will it affect the babies?