>>9863468 (pb)
Muscle spams, anon, caused by nerve root impingement due to degenerative disk disease or disk bulge (likely, if this is your first bout with lower back pain) or disk herniation. See a chiro to stop the spasms, get yourself an inversion table (passive) and begin core isolation exercises which will lessen stress placed on lower back long-term.
Inversion therapy takes gravitational pressure off the nerve roots and disks in your spine and increases the space between vertebrae. Inversion therapy is one example of the many ways in which stretching the spine (spinal traction) has been used in an attempt to relieve back pain.
But you have to first see a chiro to "unlock" your lower back (3 - 5 sessions), rest your back and take a couple of Epsom Salt baths a day. Maybe access a TENS unit (cheap) which your chiro will likely use.
Good luck.
See also: https://www.optp.com/Treat-Your-Own-Back - "The McKenzie Method"
https://youtu.be/vqzlbHsf5rw