Thank you for your query on Healthcare Magic.
This child seems to have weakness.
The causes of weakness may be due to :
1. Cerebral palsy
3. Paralytic polio
The description you told is not sufficient to say one diagnosis.
His birth history, perinatal history , and history of any CNS infections is important to come to a conclusion for his problems.
And physical examination of the child and review of his complaints and the medical history by a Pediatrician is important to diagnose the problem.
In this type of problems physiotherapy
is the mainstay of therapy.
Therefore I advise you to consult a Pediatrician
Hope I have answered your query.