Henry
Glad to hear things are improving.
I just had injections today in the SI joint because of that same tailbone area pain.
Dr. Zeegers told me that it's probably referred pain from the lumbar area and not the SI joint.
You probably just need more time for your muscle's to relearn where they are supposed to be and actually learn to relax again.
Don't over do it.
Remember that gel pack is your BFF!
Glad to hear you are improving