What Causes Sudden Change In Behavior, Anger Issues With Bed Wetting?

My son turned 6 last week and i am very worried about his behaviour it suddenly changed drematically about 6 weeks ago and seems to be getting worse, he was a loving, happy quiet little boy and not has unexplained outbursts of anger/unnecessary fearfulness/crying this is so out of character that i am worried that there could be some sort of underlying medical problem causing it. I am so confused as to what has happened to my little boy, he seems to react to any little thing his siblings do and there is just no getting through to him. We have always used Time Out which works well for his Older Sister and Younger Brother and always worked for him, but now he screams/shouts/lashes out and then when eventually completed his time out proceeds to act the same way. He has also started to wet the bed when was previously dry, its not a regular thing but its something he never done even when he was very young. Any advice would be much appreciated