My little boy 4 is out of control please help me??

My 4 year old angel has turned so since starting school in sept he is a aug baby so just turned four before staring he is'nt cheeky just how can i put it wild, i have suffered depression since having him, but i am not blaming him neva will but i feel such a failure i also have a 12 year old girl and no she was neva like this some1 please help me x