I've tried everything but still wake up on my back

I am 25 weeks- I have a wedge style pregnancy pillow and have sewn tennis balls into the backs of shirts. I fall asleep very comfortably on my side but constantly wake up on my back. I've tried sleeping with my upper body elevated but this seems awkward to me and makesit harder for me to fall asleep. And i sink down in my sleep anyways and seem to just wake up below the elevation pillow on my back. I actually prefer to fall asleep on my side but it's as of my body prefers to back sleep in my subconscious. I have pregnancy insomnia bad right now so just getting to sleep is crucial. Most times I wake up I am either sleeping directly on top of the tennis ball or the ball as moved to the side somewhat and I'm still sleeping facing upward. The scary part is I have a very active baby but anytime I wake up like this he is completely still until I roll in my side and he starts kicking again. Anytime I lay on my back in the tub or for a few minutes while awake he stops moving completely. A few times I had dreams I was suffocating and woke up and rolled over. But nothing too crazy symptom wise myself. I read back sleeping doubles the risk of still birth. I'm terrified I'm depriving him of oxygen every night. Help!!!!!