I never knew what back spasms were until 4 years ago. I thought it meant your back muscles just flickered, but no, it's extremely painful.
Wife and I were RVing with friends out at land between the lakes. 4 hour drive. After setting up the trailer, I sat down and it started hitting me and it kept getting worse. However, it started in my stomach area, then, within about 20 minutes, had wrapped around my entire core and up to my shoulders. I thought something ruptured and there wasn't a hospital anywhere near us.
I made it through the night, but I basically took an entire bottle of advil. I was scared, I really thought something major happened to one of my organs.
Went to urgent care the next day, they gave me muscle relaxers, so I stayed the entire weekend in the trailer.
Problem was, I had to tow that trailer home, the wife won't even consider it and nobody else in our group wanted to mess with towing a trailer that big.
So down the road I go, but at least once an hour I had to get on the shoulder, get out and lay flat for a while. Couldn't take the muscle relaxers, they make you drowsy. Took 8 hours to get home.
I have a great chiropractor, she got me back to normal, but it took 3 visits. That was some serious pain.