Who is this child?

Ok, I know boys will be boys. And I know that all kids have their moments of not being sweet little innocent angels. But I honestly don't know who the child living in my house is.

He has always had a bit of an attitude. An attribute I am assured (by my mother) that he got from his mother. (LOL)

Since he started kindergarten in August, he has slowly changed into a child that is virtually unrecognizable. He talks back nonstop. No matter what I say, he argues with me. If I say the sky is blue, he argues with me about it.

He has decided that it is appropriate to tell me no, and that I can't make him do .........whatever the task at hand is.

Now not that that isn't bad enough but now he is also throwing tantrums like a 2 year old. He actually got mad at a 2 year old yesterday for not sharing a ball and threw himself on the floor and threw a hissy fit!
I had to drag him out of my nieces soccer game, kicking and screaming. He was acting worse than any 2 year old could have possibly been.

Anyways, there have many a trips to sit on his bed with no toys or tv and many a talkin to. He gets disciplined. I really don't know what else to do.