I prop myself up too. Cause sleeping on my sides makes my tailbone and hips throb :-(
Just get a bunch of pillows and figure out what works for you. Don't worry about getting the expensive maternity ones either cause I have one and cheap ones and most days the cheap ones work better :-)
The best position is on your left side because it provides the best circulation to the baby. When my side hurt in the middle of the night I prop pillows so I'm almost sitting up and I'm not flat on my back.
You may want to use pillows too. You can placeva smaller one under your tummy while you're on your side.
It's normal to be concerned...I was the same with my first but your baby is perfectly safe in there. You're actually meant to sleep on your sides...especially your left side as it improves blood flow to the baby and placenta and helps with your own circulation. You really shouldn't be sleeping on your back as this restricts blood flow to baby. Trust me your baby will not be compressed :) good luck and try and get proper sleep while you still can ;)