Thank you for your query,
My first concern for his weight loss
, excessive thirsty, excessive intake of oral fluids, and bed wetting is first to rule out is Diabetes Mellitus
As these are the classical symptoms of presentation of Diabetes in this age group children.
His urine to be examined for glucose and ketone bodies
Blood to be checked for glucose levels.
Consult immediately your Pediatrician
and go for evaluation as early as possible.
Hope I have answered your query.