Almost two years ago, I woke up in the middle of the night knowing something very, very bad had happened and I wasn't too sure what it was. I rolled out of bed on to the floor and had to crawl into the bathroom - I knew I was in bad shape but didn't know if it would correct itself and I didn't want to wake up my wife. I made it to the bathroom and started to lose consciousness from the pain. I was going vagal and basically blacking out. The funny thing - in hindsight, it's funny - is that I'd been in this position with other types of pain before and knew exactly what was going on so I literally talked myself through it - " hands are numb and tingling ... tunnel vision coming on ... okay, breathe slowly .... get some water ... okay, here comes the flop sweat ... under control ..." Anyway, I eventually fell asleep on the bathrrom floor unabel to move. When I woke up, I was able to move slightly and I downplayed the whole thing to my wife. I went to see a few different doctors - my chiropractor helped make it manageable, my regular doctor wanted to put me on Percocet. But it eventually went away. Then it happened again like three times between the end of summer 2016 and early 2017. Eventually, my wife talked me into going to see a specialist. Turns out I had two herniated discs (what I experienced that first time was the actual herniation of one of them - the specialist said that based on my description I probably experienced the moment the casing just ripped open and my spine compressed like a deflated balloon in the lower left side of that one vertebra.)
I mention this all for one reason - there is some hope. What you are describing actually sounds pretty similar to herniation. As bad as that was - and when it would flare up, I was basically immobile for days at a time - there are treatments. On the extreme end is surgery, but my doctor recommended we try the cortisone shots first. The shots are a cycle of three, and you don't have to get them all in one cycle (but once you've had the three, you can't get any more.) I did get the full three (basically one shot every two or three weeks.) And it helped a lot. It isn't perfect, but it's allowed me to be mobile again. The doctor did say that it's not a cure and that's right - over time, I am going to eventually return to the limited movement I had before. But for now, it was a far better option than surgery, which is always a risk. Lately, I've noticed that I'm feeling a bit stiffer than I did after the shots once again, but I am picking up more yoga classes again to try to help that. I figure it's the combination of things - like the treatments I've had, extra yoga for flexibility, therapeutic massage once a month, and being smart about how stupid I'm willing to be on the bike at my age - that are going to keep me rolling now.
So if I were you, I'd first talk to a specialist. Find out what exactly is happening with you and what your best options are. Then put together a plan to help you maintain that flexibility and don't tax your back too much. For me, this is all in service of being able to take part in the activities I enjoy, but for you it's probably a lot more in addition to that, since I figure you'd want to be able to stay mobile to enjoy life with your family. You need to look into ways to make this manageable and better now because if it is anything like what I had, it's going to get worse and more frequent as time passes.
Good luck, Dave!