Question about sleeping

I’m about 21 weeks and I always catch myself asleep on my back. I fall asleep in my sides but I always tilt backwards onto my back and it really worry’s be because I know that’s not recommended because of blood flow and pressure. Is my baby gonna be okay? I’m worrying about it a lot and I just need some comfort about it. My stomach tends to be sore after words but it normally always is when I wake up. The baby stays up all night kicking and and I guess sleeps through the day. Thanks for all the answers!