Welcome to HCM,
What do you mean by internal fever because if your body temperature is normal and clinical examination is normal and as per your communication investigations are also normal and do not show any abnormality.
You may be having generalized weakness and tiredness
and body ache which is felt by you as fever in such cases possibilities are you have chronic fatigue syndrome
or have masked depression
along with anxiety but both needs evaluation by physician and/or Psychiatrist
if required further investigations like Thyroid function,B12 level, vitamin D3
level if not already done detail psychological analysis will help to know diagnosis and then therapeutic trial of suitable antidepressant and pain modulators will be required to treat you.
Hope once you are treated properly and for long period you will certainly improve
Please take care