I can’t help but lay on my back

I’m 23 weeks pregnant, and for some reason I just can’t not sleep in my back! I wake up on my back. Of course if I’m uncomfortable I move in my sleep. But I try my best to stay on my side! Is it that bad I hear everyone saying it’s a horrible way to sleep. I didn’t have this issue with my previous pregnancy, I slept on my side the whole time. This pregnancy it’s an issue I can’t help it. Advice? My fiancé is already out of bed, abd I have my 2 year old sleeping with me. He’s refusing To sleep in his own bed for now. So pillow behind me isn’t an option yet 🙄🙄🙄