J.J.
Did anything change in his life about 3-4 weeks ago? Did he just start school? Does he have a new teacher or childcare person? Could he be dealing with a bully in some area of his life?
Here are some other resources which I hope might be helpful for you...
http://www.askdrsears.com/html/7/T070100.asp
http://www.askdrsears.com/html/6/T060900.asp
http://www.askdrsears.com/html/6/t063300.asp
http://www.askdrsears.com/html/6/T060100.asp
Best wishes,
J.