Body
The brain just doesn't invent pain. 'Without brain no pain' but also 'without body no pain'. There is no evidence that pain exists without nociception (signals of homeostasis disturbance). Enhanced sensitivity often, but by no means always, plays a role in chronic pain, but is never solely responsible for a pain experience. If X-rays and MRIs do not show anything special, this does not mean that it all comes from the brain, the source of the complaints is probably in the fascia. The Princess and the Pea may have been very sensitive, but there really was a pea.
The body is made up of cells and connective tissue. With the exception of bones and blood, all connective tissue falls under the term 'fascia'. Blood contains no nocisensors, bone very little. It is therefore logical to assume that virtually all nociception from thefasciacomes. Mechanosensors can register the stretch or pressure on the collagen structures, chemosensors will measure the chemical environment of the interstitial fluid (ground substance). Mechanosensors have a very high stimulus threshold, we can lift heavy weights without pain. But if these sensors are sensitized by central and/or local (= chemical) sensitization, stress can lead to pain. If someone indicates a local pain during stress, then it is most likely that there is a local disturbance of the chemical environment. If someone reports a very diffuse pain, central sensitization could play a greater role.
It does not appear that there is pure physical pain or pure psychological pain, it is probably always a mix.