Suggest Remedy For Behavioural Problem In A Toddler

Hello, I have a 5 year old who constantly cries and whines about everything and is called from school to get picked up for behavior problems like this and it is quite frequent. He is also very hyper and when I tell him not to do something he does it anyway and says he does not know why he did it. I am concerned with his unusual behavior. What may be going on?