Теория:

Study some information about negative sentences in Past Perfect Continuous.
 
Для образования Past Perfect Continuous необходимо использовать структуру had been и основной глагол с окончанием -ing.
Subject \(+\) had \(+\) been \(+\) Ving \(+\) other parts of the sentence.
Для построения отрицательного предложения нужно использовать следующий порядок слов:
subject \(+\) had \(+\) not \(+\) been \(+\) Ving \(+\) other parts of the sentence.
Examples:
 
Mary had not (hadn't) been learning Maths all day. She was free.
  
              I                  
                                                               had not (hadn't) been studying
 
       
            you
 
had not (hadn't) been studying
 
he, she, it
 
had not (hadn't) been studying
 
we
 
had not (hadn't) been studying
 
You
 
had not (hadn't) been studying
 
They
 
had not (hadn't) been studying