HI-I am the primary caregiver for my wife who has similar issues. Did your doctors tell you much about MGUS? It's the precursor for Multiple Myeloma. Both start when your marrow creates abnormal protein cells that overpopulate the bone marrow space. In the process they leach calcium out of the bones that enters the blood supply causing downstream issues while weakening bones.
My wife had L1 repaired by kyphoplasty last summer. She also had fractures of T7 & T8 that were mending themselves and weren't repaired by surgery. I'm not a medical professional, but have learned a lot about MGUS/MM. You are fortunate you found your issues as early as you did as MM is a silent disease. In hindsight my wife had unexplained leg fractures 3 plus years ago. We just attributed them to age and having a job requiring lots of lifting. Between the leg and spine fractures she also had several rib fractures. Our picture was slow to evolve into an actual diagnosis. In fact we diagnosed her before the doctors did. Most importantly for you, if you've not had recent blood and urine tests, you need to have them. Assuming I'm on the right track, you'll eventually have genetic testing too. All 3 parts were needed for us to get our confirmed MM diagnosis (imaging, labs and genetics).
A good source for MGUS/MM info is the Multiple Myeloma Research Foundation (MMRF). Good luck with your investigation. There are several good relatively recent therapies to slow disease progression.
Your hematologist should have a network for you to consult and treat with, if/when necessary. MGUS is sometimes only watched and not immediately treated. Although my wife has full blown MM that had to be dealt with post haste.
Regards

My husband has the same issues and he's only 38 is lower spine. His cartilage in between his vertebrae are disappearing fast so it's almost bone on bone. he got off his my pain medicine because he got sick of it. Lyrica honestly I don't think it's going to help it's a nerve blocker of course but at the same time it can make you feel like you're drunk and you have more of a chance of falling then you would not taking it. Now my husband wanted me to tell you since you do have the lower vertebrae problems is to go to the gym. Nothing heavy just on physical therapy machines. he said making your muscles around your spine stronger helps tremendously. maybe in the next 10-15 years they'll figure out something for yourself and my man. Ty

Also I forgot to mention why don't you talk to your doctor about a pain pump. It looks kind of like a diabetic pump but it puts medication into your system when needed. It helps my friend's dad 100%.

I have compassion for where you are. My husband has multiple myeloma with collapsed vertebrae in his lower spine. My own spine at 50 was like yours, from lack of estrogen after breast cancer in my 30s. It was not really addressed for a few years as I was not under the care of an oncologist anymore. I resumed care with a medical oncologist who finally addresses this. I do take injections without incident and it is helping. Yes, I feel a little achy the day after but that is all. I know this does not really answer the “why” for you, but maybe knowing you are not alone and there are things that help can ease your mind a bit.