I know that sometime in the 2nd tri you're supposed to stop sleeping on your back...but when is that supposed to happen? I'm about 15 weeks, and the only way I can fall asleep is on my back. I sometimes end up on my side, but if I wake up in the middle of the night and can't go back to sleep, being on my back is the only way that does it. Is this really bad for the baby? Basically, at what point do I need to break down and get one of those pillow thingies to help me stay in one position?