I had bilateral total hip replacements last year (about 6 months apart) through the anterior approach and I am primarily a side and stomach sleeper so I completely understand not being comfortable on your back! While I was technically allowed to sleep on my side after surgery it really wasn’t possible because it was too uncomfortable. I found that the first couple of weeks I was most comfortable in my powered recliner chair with a pillow under my surgery leg and wedged against the outside of my surgery leg to keep it from rotating out. Within about two weeks, I was able to be in my bed and I would use a pillow or a memory foam wedge underneath my surgery leg and also a pillows wedges against me to keep me from getting the urge to turn on my side. You will definitely be able to get back to side sleeping but there are some adjustments you will need to make until you can get to that point where you are comfortable/healed. Good luck with your appointment tomorrow!