In this scene, Lady Macbeth wants to be Queen and her husband (Macbeth) wants to be king. Although, Lady Macbeth did not think that Macbeth was strong enough. Therefor, Lady Macbeth makes a statemet saying ‘Unsex me here’ because she knows that she is not mentaly strong enough to kill King Duncan and she believes  that if she was a man, she could kill him