The list of what can cause chronic pain is enormous. Everything from arthritis, spinal/nerve injuries, ulcers, MS, carpel tunnel, bone disease, post-surgery...
Other times it can be related to our mental health, so this means that we cannot necessarily see biologically what's happening, but stress and stressful times in our life can create chronic pain.
There can be many causes of chronic pain, and it is recommended you visit your local doctor for a proper diagnosis or check up just in case your chronic pain is part of a bigger illness. Chronic pain can come from chronic conditions, diseases, illnesses, or even old injuries that didn't heal over right. Tight muscles, bad posture, pinched nerves, etc. Sometimes, chronic pain can even be caused by mental health and stress. Mental illnesses like PTSD or anxiety can cause hyper-vigilance because your muscles are constantly tensed in preparation for a fight or flight response. Getting a professional opinion on the specific cause of your chronic pain is important, and more reliable than any google search can be. Pain is a presentation that something is wrong with your body, take care of it and treat it accordingly!