I wonder if aches and pains feel more severe than they normally would in conditions like ME/CFS as a result of
sickness behavior. As many people know, Michael VanElzakker has proposed that ME/CFS may in fact be due to chronic activation of the sickness behavior response, this activation arising from a chronic infection.
The symptoms of sickness behavior are numerous, and include fatigue, malaise, cognitive impairment, depression; but in particular, sickness behavior involves
increased hyperalgesia — that is,
abnormally heightened sensitivity to pain. Ref:
here.
So if ME/CFS does indeed involve chronic sickness behavior, then you might expect not only to have real pain (from say an enteroviral muscle infection or joint inflammation), but also at the same time, a heightened sensitivity to that pain.
In other words, there may be a double-whammy effect in ME/CFS, with this disease not only creating actual physical pain, but on top of that, this disease may turn up the "pain volume control" in the brain, such that physical pain feels worse than it would normally be.
In hyperalgesia, the pain signals from the body are not altered, but these signals are amplified much more than normal when they reach the brain.
Many conditions of medically unexplained symptoms, like ME/CFS, IBS and interstitial cystitis, have been linked to chronic infections, and these infections could be triggering the sickness behavior response, and thus hyperalgesia.
So this sickness behavior mechanism of increased hyperalgesia might actually play a role in pain catastrophizing.
Wikipedia describes pain catastrophizing thusly:
Pain catastrophizing is the tendency to describe a pain experience in more exaggerated terms than the average person, to ruminate on it more (e.g., "I kept thinking 'this is terrible'"), and/or to feel more helpless about the experience
If due to chronic sickness behavior, someone has increased hyperalgesia, with their brain's "pain volume control" turned right up, you might well expect them to describe a pain experience in more exaggerated terms than the average person — because with the hyperalgesia, that's exactly how they are feeling the pain.
An analogy for hyperalgesia might be putting a powerful hearing aid into the ears of someone with normal hearing. Now that person will experience any sounds from the environment in a greatly amplified way. Naturally, when that person talks about their experience of environmental sounds, they are certainly going to comment about how damn loud they are. And they may well ruminate of how damn loud the world is.
Likewise if your pain amplifier is turned to full volume, you are certainly going to comment about how damn bad the pain is, and may well ruminate on how bad pain can be.