At the Physical level, chemically speaking :
“Pain is a message, to the Brain, that something is wrong”
Brain is in direct intermediary of soul (with subconscious mind) and physical body.
Physical pains are the ones which have moved down the level of physical body and give unpleasant physical sensation.
While so called undiagnosed pains, which make you look like faker in front of others, are actually early signs of some issue in Astral body. This message is not detected in nervous system, brain does not get message from physical body but mind does get message from astral body.