Macbeth has some difficulty coping with reality in Act 2. He has been coaxed into killing Duncan by his wife after the witches told him he was going to be king. Yet Macbeth begins to have doubts. Through either the activity of his brain or magic, he starts seeing and hearing things.
Art thou not, fatal vision, sensible
To feeling as to sight? Or art thou but(45)
A dagger of the mind, a false creation,
Proceeding from the heat-oppressed brain? (Act 2, scene 1, p. 27)
Macbeth begins to doubt his senses. Wouldn’t you if a dagger suddenly floated in front of you? Macbeth is disturbed by the dagger, and has a conversation with himself about it.
Thou marshall'st me the way that I was going,(50)
And such an instrument I was to use. (Act 2, scene 1, p. 27)
Ultimately, Macbeth seems to think that the dagger is encouraging or goading him on to commit the crime. When he hears Lady Macbeth’s signal, he acts.
This is not the end of Macbeth’s hallucinations though. In Scene 2, Macbeth hallucinates again. This time he is hearing things.
There's one did laugh in's sleep, and one cried,(30)
That they did wake each other: I stood and heard them:
But they did say their prayers and address'd them
Again to sleep. (Act 2, Scene 2, p. 29)
In this case, Macbeth imagines that he hears someone calling out murder, and in fact the voice says that he has “murdered sleep” (p. 30). This demonstrates that the dagger before he killed Duncan was not an isolated incident, and Macbeth still feels uneasy after he commits the deed.
Macbeth's halluccination's were dagger's. The fact that Lady Macbeth has forced Macbeth into wanting to kill Duncan to become king, suggests she is making him sound as if he's a big chicken because he's afraid of killing Duncan. Macbeth has been forced into accepting this challenge of murdering Duncan to become king, at that point, he starts hallucinating daggers. He starts getting paranoid, shakey and nervous of what their plans for Duncan are.
I really hope this has answered your question! I'm on Act 3 Scene 1 now in school, so I'm kind of ahead.