Your son must be having a bad virus going on for the past 2 weeks.
Did you see a doctor? If not, please have him seen by a Pediatrician
as its 2 weeks now.
Many viral illnesses present with aches everywhere and tummy pain too due to gastritis
Since both his intake and activity are not okay, I would suggest that you see a doctor soon, have basic blood tests like Complete blood count
, CRP done along with urine routine and get him treated accordingly.
Till you see your doctor, give him plenty of fluids- plain water, juice, milk, soups etc.
He might need oral Acetaminophen
in a dose of 15mg /kg/dose repeated 3 to 4 times a day for pain in his limbs
His tummy ache needs to be assessed by a doctor and treated accordingly.
Hope my answer helps you.
Wish a speedy recovery for your son.