What is happening to Macbeth in lines 40-42 and what advice does Lady Macbeth give him in lines 45-46?

Macbeth is losing whatever control he might have had. He laments that he is at the mercy of his destroyed conscience. He fears that he will never sleep again after the deed that he has performed. L. Macbeth goes with her old stand by when dealing with her husband. She questions his manhood. She is shocked to find that he still holds the bloody daggers.