This video is a bit of work to get through, but it may help you figure out what is causing your pain. It is more likely to be something that can be remedied. https://www.youtube.com/watch
It must have been really intense to end up in hospital.
I'm not sure about the "square thing you put into the nerve." The NP may have been referring to a nerve stimualtor. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/treating-pain-with-spinal-cord-stimulators,
Usually with low back pain you don't have cervical, thoracic, or pelvic MRIs. All of these areas can cause low back pain. I can get sharp back pain from the SI joint, but even imaging that doesn't always reveal the disjoint.
I would also suggest that you consider seeing a chiropractor. The perform the best hands on assessment.
Those grandkids are lucky.