I keep waking up on my back

Amanda • mommy of a 6 year old princess now expecting a prince💙👶🏽
I've always been a back sleeper & for the past few weeks I've tried falling asleep on my side and then I end up waking up on my back having trouble breathing. I can't really fit a pillow behind me because my fiancé & I share a queen bed n there's not much room between us :/