Macbeth... Sane or Insane...0_o

At this point in the book I believe that Macbeth is insane. At times he seems as if he's sane to a person who doesn't pay much attention to him. But when you really pay attention and read deep between the lines you can't help but think he's insane. Why you say??? Because while reading Act 2 Scene1 pg 53 Macbeth is alone in the room talking among him self about the crime he will soon commit. Grasping at the imaginary dagger that is in front of him & later pulling the same dagger from his pocket. Or even when the bell rings and to himself he says "I'm going now. This is as good as done. The bell is telling me to do it. Don't listen to the bell, Duncan, because it summons you either to heaven or to hell". My point being how can you read all this with out believing Macbeth has driven him self to insanity. All from planning to commit such a crime while at the same time having to face what he has done and its consequences.