My 3 years old son has become very stubborn...doesn't listens to me or his dad unless we shout at him. We tell him don't do he will do it and show. How do I explain to him?

Reckon your son is at the age where he is testing his limits and boundaries with figures of authority, which is perfectly normal. While shouting at him seems a quick fix method, it might impact him negatively in the long run, as he gets older. It is not desirable if your son grows up only listening to you when you raise your voice. Be patient and explain to him that his behaviour is not acceptable. You can try giving him a time-out (ie take away his favourite toy or tv privileges) if he doesn't do what you say. Make him understand that there are consequences to his negative actions. He'll come around soon, I'm sure :)