First,
big hugs to you! Several years ago due to a riding accident I broke 3 bones in my lower back. Took 10 weeks to heal (no surgery needed thank goodness). When given the okay to ride, I mounted T my tried and true girl and burst into tears. I was a wreck! Never felt such terror and so very vulnerable in my life and I had had riding accidents before.
How I got over it was one step at a time. I rode T where I could and feel in control ie.the round pen or the paddock. An arena would have seemed way to large at the time. Just kept at it, walk only for quite a while, and then something just clicked and I was back.
Now at the same time I had a youngster that I was just starting to saddle train. With the help of friends, I was able to ride him and trust in the training I had done with him. Yes truth be told, when on Walka, I still get in the back of my mind that fear, but I get stronger in my mind and push that negativity back so it doesn't interfere with my riding .
It's not easy. We are not children anymore and we have so many responsibilities next to us in that saddle...mortgages, car payments, family to care for ect... that we are very aware of our fragility. But we also love riding and horses. Trust your skill, ride where you feel in control no matter how small an area and if you need to have a friend next to you on the ground or on a horse next to you. Take your time, it will come.
Hope I helped a little. It's a journey but well worth it.