I came off my gelding in January and my shoulder still isn't right. I've been to the doctor but I still suffer pain on most days. Both my doctor and I agree that surgery isn't an option right now for a few reasons. I'm working through therapy and have been riding but I totally understand your fear. I've been very anxious about riding since my unofficial dismount so I've been taking things very very slowly.
I have decided that what I needed was to build a framework of small successes that would allow me to feel better about my seat, my horse and generally about my ability and safety. We started with simply mounting and dismounting several times. That was enough for one lesson. Then we moved toward walking in the paddock and a few simple commands like stop and backing. That was enough for a second lesson. Using this stepping stone method I have been able to rebuild my confidence while letting my horse know that I'm still in control and we have built a number of successful rides.
Yesterday, for the first time since I brought this boy home, we untacked and I was able to proudly display a wet saddle pad: a long and successful ride. We still have a few barriers to work through but I've back in the saddle, riding with care and ease while enjoying myself and my horse again.
I hope you can work out your anxiety, safely and joyfully. Be well and be blessed.
"The road goes ever on and on, down from the door where it began. Now far ahead the road has gone, and I must follow, if I can." J.R.R. Tolkien