Question

how do we come to know that there is something wrong with our body

Answer 1

If something is wrong within your body, your body will start to send signs which are also known as symptoms for example if you begin to feel light headed your blood pressure may be low. If you start to experience symptoms you should go to the doctor.

Answer 2

We will experience some symptoms if there is something wrong with our body.
For example, some symptoms of fever are : Chills, common cold, and cough.
Hope dis helps