Periodic high fever 103-105. Happens!

My son who is 3 years old weight nearly 13 kg. He is very active and energetic. But he got fever due to infection once in 2 or 3 months. He got very high fever 103-105 f. Even sometimes alone paracetamol syrup doesn't work. The fever starts from back head  then his forehead face and reach till feet. And feel like warm water. His ear and face becomes red. Eyes fill with tears. And he feels hot and remove blanket. Even i remove his extra clothing. Every time fever subside 5-6 days. Even ibugesic plus is given still it takes 5-6 days . And during these episodes child health goes down . Because he does not eat properly only drink water milk , snacks but not proper food. And when fever settled then cough episodes start . It takes 10-15 days to recover. And about 1 month he suffers and we also suffer. But my question is that why he get such high fever in such period of time. He becomes very weak. And as soon as he recover again fever episode starts. How to deal with it. Why this happens