Suggest Treatment For Constant Pain In Lower Back Post Injury

Question : Good evening. Approximately three years ago, I moved a bucket of landscaping rocks (on wheels) with my leg pushing outward to the side. Immediately, I felt a "tear/electrical zap" in my bottom area (possibly sacrum area) (between the low back and bottom). I have been in constant pain ever since which was aggrevated when I got rear-ended a few months ago. My doc said it was muscle spasm so did PT, pain shots/injections, anti-inflammatory meds. Have TENS unit I use. I also have a gap in my SI joint, but do not know if that is related or not. I also wear an SI belt. I had an MRI of lumbar spine done last week and doc said it was fine, just showed "minor arthritic changes". You can clearly see an issue with a facet joint on the MRI...is this what doctor considers minor arthritic changes? Could this be the cause of all of my pain. I can barely walk, sit or stand and if I do, I get fatigued after about 10 minutes. Doc said I just need to "move" more. How can I move more if it takes me a week to recoup after doing anything. For example, I had PT and then a doctor appointment right after. So long day and lots of poking. It literally took me a week to be able to walk about that. Is my doctor missing something or could it really be muscle related or SI related. This area that hurts feels like someone sliced me open and laid me out like a fish. Walking and sitting only causes more pain. Thank you!