Past Perfect Continuous(Progressive)

The past perfect continuous (also called past perfect progressive) is a verb tense which is used to show that an action started in the past and continued up to another point in the past.

Past Perfect Continuous Forms
The past perfect continuous is formed using had + been + present participle. Questions are indicated by inverting the subject and had. Negatives are made with not
Statement: You had been waiting there for more than two hours when she finally arrived.
Question: Had you been waiting there for more than two hours when she finally arrived?
Negative: You had not been waiting there for more than two hours when she finally arrived.

Past
Future
Present
Past
Future
Present
Past Perfect Continuous
Present Perfect Continuous
Action started in the past and continued up to another point in the past
Action started in the past and has continued up until now

"For five minutes" and "for two weeks" are both durations which can be used with the past perfect continuous. Notice that this is related to the present perfect continuous; however, the duration does not continue until now, it stops before something else in the past.
They had been talking for over an hour before Tony arrived.
She had been working at that company for three years when it went out of business.
How long had you been waiting to get on the bus?
Mike wanted to sit down because he had been standing all day at work.
James had been teaching at the university for more than a year before he left for Asia.
A: How long had you been studying Turkish before you moved to Ankara?
B: I had not been studying Turkish very long.

Using the past perfect continuous before another action in the past is a good way to show cause and effect.
Jason was tired because he had been jogging.
Sam gained weight because he had been overeating.
Betty failed the final test because she had not been attending class.
Past
Future
Present

REMEMBER Non-Continuous Verbs/ Mixed Verbs
It is important to remember that Non-continuous verbs cannot be used in any continuous tenses. Also, certain non-continuous meanings for mixed verbs cannot be used in continuous tenses. Instead of using past perfect continuous with these verbs, you must use past perfect.
The motorcycle had been belonging to George for years before Tina bought it. Not Correct
The motorcycle had belonged to George for years before Tina bought it. Correct

Non-continuous verbs
These verbs are rarely used in continuous tenses. They include:
Abstract Verbs
to be, to want, to cost, to seem, to need, to care, to contain, to owe, to exist...
Possession Verbs
to possess, to own, to belong...
Emotion Verbs
to like, to love, to hate, to dislike, to fear, to envy, to mind...
He is needing help now. Not Correct
He needs help now. Correct
He is wanting a drink now. Not Correct
He wants a drink now. Correct

ADVERB PLACEMENT
for grammar adverbs such as: always, only, never, ever, still, just, etc.
You had only been waiting there for a few minutes when she arrived.
Had you only been waiting there for a few minutes when she arrived?
ACTIVE / PASSIVE
Chef Jones had been preparing the restaurant's fantastic dinners for two years before he moved to Paris. Active
The restaurant's fantastic dinners had been being prepared by Chef Jones for two years before he moved to Paris. Passive
NOTE: Passive forms of the past perfect continuous are not common.