Just to say, take it seriously. I've had it for years on and off but the last time it was awful. Caused muscle spasms and a pal who is medically aware rang 999 as I was in so much pain and couldn't move. They put me onto a doctor who arranged high strength codeine and low dose of diazepam which relieved the spasms and helped a lot.
Now, nearly a year on, I'm still being very careful. Moved some pallets a few days ago and end up having to take a diazepam to get to sleep as it was cramping again. My doctor doesn't like prescribing addictive drugs
and I'm down to 6 pills
The exercises do work, but don't strain. My osteopath helped a lot too - until lockdown stopped me going. Good luck.