Think of your brain as holding a master volume knob for all physical sensations. When you are stressed, worried, or exhausted, your entire nervous system enters a state of high alert. Consequently, your brain turns that volume knob all the way up to ten.
A harmless, normal physical movement or standard physical sensation that should feel completely quiet is suddenly amplified into a loud, painful scream. This process is a software glitch, rather than a hardware break.