Grammar - Past Perfect Continuous Tense

Past Perfect Continuous Tense

Usage
he past perfect continuous tense (also known as the past perfect progressive tense) shows that an action that started in the past continued up until another time in the past. The past perfect continuous tense is constructed using:
had been + the verb’s present participle (root + -ing).

Unlike the present perfect continuous, which indicates an action that began in the past and continued up to the present, the past perfect continuous is a verb tense that indicates something that began in the past, continued in the past, and also ended at a defined point in the past.

He had been drinking milk out the carton when Mom walked into the kitchen.
I had been working at the company for five years when I got the promotion.
Keywords
When, for, since, and before are words that you may see used alongside the past perfect continuous tense.

Martha had been walking three miles a day before she broke her leg.
The program that was terminated had been working well since 1945.
Note:
The short form is: 'd been verb-ing. Be careful, because the short form for 'would' is also 'd. However, 'would' is always followed by the infinitive, but 'had' is followed by the past participle.

Next, the negative form:
I had not been trying (I hadn't been..)
You had not been working (you hadn't been..)

'Yes / no' questions:
Had I been working?
Had you been sleeping?

'Wh' questions:
Where had I been working?
How long had you been sleeping?