I echo others' thoughts expressed also on other threads on why the name of the disease is not the primary issue that needs to be addressed at the present stage.
(As usual, it took me some time to write this post so apologies if parts are redundant by now. Also, as I read mostly on the forum without being logged-in so I'm not tempted to comment too often, I include here a collective

for the discussion here and on other threads. )
In my experience, health care professionals tended to get more interested and to listen more, when I referred to the uncertainties regarding ME/CFS but also described the clear pattern of PEM I experience and mentioned the treatments I tried to no avail.
These treatments that I tried to no avail however included psychotherapy, a variety of antidepressants, and exercise. Also, what perhaps helped being not perceived as the typical 'psychosomatic' patient was that I seem to be more lucky than many other pwME with respect to being able to do some gentle exercise 2-3 times a week.
After PEM-triggered crashes I actually often could get back to my pre-crash level of fitness to a certain degree by resuming some very gentle exercise, including short walks or short, light cycling, but I never got over the point that I could do more than 30 minutes of light exercise without needing to lie down immediately afterwards, plus, if I did more on the same day, delayed PEM with flue-like sickness. (So still very far way from my pre-illness level of fitness.)
So I think even the best term for our illness still needs additional explaining, simply because how the illness presents itself doesn't fit in any current conception of disease.
It might be impossible to convey the utter disproportion and diversity of reactions to activity pwME experience, and also the range of severity, in any term.
With regard to 'fatigue' as belittling the illness: It could be helpful that fatigue in other chronic illness is taken more seriously by now. When large MS or cancer charities state that many patients experience fatigue as the most debilitating of their symptoms, then this kind of fatigue can't be harmless.
I think 'ME/CFS' is the best term we have for now. I conveys the uncertainty about the illness well and the combination does not allow to conceive what we suffer from as just being tired all the time (even if being extremely tired all the time can be pretty debilitating, too).
The only alternative name I could think of at this stage is -- '/Disease' (SlashD).
