I CANNOT Stop Laying on My Back 😭

Kat
Has anyone else heard that we aren't supposed to lay on our backs for too long while pregnant? Something about the weight of baby and the uterus putting pressure on the artery that supplies the uterus... 
I am constantly waking up on my back! I have a pillow that I sleep against, but I just keep moving it in my sleep 😡 
Anyone else having similar issues??Â