How do I avoid rolling over onto my back while asleep?

Nabi • Mom of 2: girl born in 2015 and boy in 2019
I know that once the belly gets bigger,  you're not supposed to sleep on your back anymore. I am 18 weeks now and trying to train myself. I am definitely a back sleeper and sleeping on my side has never been comfortable to me. At first I could not even fall asleep on my side. It got better when I bought a pregnancy pillow (Snoogle). But even when I fall asleep on my side and I think there is no way I can turn around in this giant contraption, I will still wake up on my back. Has anyone found a solution that worked? Thanks!