In Macbeth (Act 3 Scene 2) how do we know that Macbeth is disturbed?

First of all, Lady Macbeth notices that her husband is
disturbed.  She wonders why he has been keeping to himself and worrying over the past.  She tries
to cheer him up with

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Things without all
remedy

Shoud be without regard; what's done is
done.

Macbeth replies, though, that he
is not happy, and uses a metaphor declaring

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We have scotched the snake, not killed
it.

Killing Duncan has not brought an
end to Macbeth's worries.  He is worried because Banquo still lives.  He admits that he has not
slept well, that "terrible dreams" have disturbed his sleep, and that his mind is "full of
scorpions."

Guilt and fear plague Macbeth, so he focuses on Banquo.
 He thinks killing Banquo will give him some relief from his fears of being found out and fears
that he killed Duncan in vain.