noun
1
BAD : I'm sorry to cause you so many troubles.
GOOD : I'm sorry to cause you so much trouble.
BAD : I'm having some troubles with my supervisor.
GOOD : I'm having some trouble with my supervisor.
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Trouble (= difficulties or problems) is an uncountable noun: 'I hope you didn't have any trouble getting here.' 'His back has been giving him a lot of trouble recently.'
Note the alternative: 'I'm sorry to cause you so many problems.'
2
BAD : Sometimes my little brother is a real trouble.
GOOD : Sometimes my little brother is a real nuisance.
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A person or thing that annoys you or gives you problems is a nuisance : 'The post office closes early today, which is a bit of a nuisance.' 'Alan! Stop being a nuisance and find something to do!'