I suffered from chronic pain symptoms for almost 10 years (was unable play the piano and type on the keyboard) until I realized it was 100% psychosomatic.
i greatly admire schubiner and sarno for exploring this issue but their limits are clear, and they admit it themselves. relatively few patients (i think for sarno it was like 20%?) will "accept the diagnosis." and why should they? again, in 80% of patients the crisis of jouissance is not sharp enough to really investigate their unconscious. and of course in many of those 20% of patients (yourself and myself included) the jouissance is displaced elsewhere, perhaps to somewhere much less obvious than chronic lower back pain.
When someone believes they have a disorder for many years/decades it becomes a part of their identity. Admitting they were wrong means that they needlessly caused suffering to themselves. It is embarrassing and emotionally painful.
They become instantly defensive, and hostile towards anyone offering alternative explanations.
but i think for many neurotic people (and most of us are indeed neurotic) the syndrome (i use lacan's jouissance) serves its purpose just fine. so don't you dare take it from them.
e.g. if you happen to have blood work from a patient pre-CFS and post-CFS it's very, very common to see a raised T-cell count and an immune response against the Epstein-Barr virus (or some other retrovirus) in the post-CFS that isn't there pre-CFS.
Of course, it's not a great diagnostic tool because you need the patient to have had some blood work just before they got sick. But it does make the "it's all just psychosomatic for everyone" argument a bit unlikely.
But the stigma attached to mental illness is real, so many/most sufferers are not at all receptive to this advice.
Just a short period of observing people who suffer from these syndromes makes it very clear that this is a psychological issue. There is a whole cluster of these vague illnesses that afflict a subset of the population with predictable psychological and demographic attributes. Nothing about their physical mechanics is in any way similar; the common mechanism is psychological.