Thanks for writing to the forum!
This could be due to chronic fatigue syndrome or fibromyalgia. However it could also be due to anemia, low blood sugar, diabetes, hypothyroid state or vitamin deficiencies especially Vit B12. There is a chance that you have compression of the spinal nerves in the cervical spine region. This can happen due to overuse of computers, work involving straining of neck, canal stenosis, bone disease, spondylosis etc. Please consult an orthopedic specialist or a neurologist.
I think you should discuss these possibilities with your doctor. It is difficult to comment beyond this without examining. A comprehensive investigation is required keeping all the points in mind.
Hope this helps. Please let me know if there is any thing else and do keep me posted. Take care!