Hello and good afternoon.
What you have sounds like mechanical back pain. It is associated with spasm of the back muscles due to strain on the back.
It is not an injury, but the body's response to prevent injury. It is a result of bad posture or over exertion or a combination of both.
Your Xray apears very appropriate for a 36 year old. Nothing out of the ordinary seen, except the fact that your back muscles are in spasm.
Next Steps
Initial treatment involves rest and pain relief.
The medications that you are taking will provide temporary relief of symptoms, but it is not advisable to take them excessively. You should rest your back and apply hot bag to relieve the spasm. If excessive pain, you can visit a physiotherapist for IFT and/or TENS therapy which will provide pain relief. Usually the pain will go away after a few days of rest and treatment.
Once pain subsides, you must start physiotherapy for strengthening the back and core muscles. Also, please adopt healthy posture practices to prevent straining your back. You can find guidelines for the same by searching on any online search engine.
Health Tips
Avoid sitting upright for more than an hour at a stretch, if your work involves sitting at a desk, try to get up and walk for a few minutes every hour. If possible, take a break and rest at home. Avoid bending forward or lifting any kind of heavy weight.