I am also a "side sleeper".
I had great difficulty in hospital having to lie on my back and not move -I never did get used to it.
When I was younger I used to sleep on my stomach however now that I am ancient, or as it is correctly termed, "at old age", I cannot sleep on my stomach as my neck does not like it.
Had a test a few years ago and had to lie on my stomach and not move for 30 minutes and it nearly killed me as my neck just will not move as it used to!