Over working is very subjective... but you will know it once you
start feeling inadequate, being overwhelmed with so much work to
do, not being able to cope, rushing for deadlines (start to panic)
and some may even depict symptoms of depression...
There is clinically no specific symptoms to point to over-working.
There are a variety of presentations, suffice to say, some presents
psychologically while some physically.
Psychologically as in psychosomatic symptoms when the person claims
of having abdominal pain, but with extensive investigations, found
that there is actually nothing organically wrong with it.
Physical symptoms may involve backache and neck pain...