Present Perfect Continuous
The past perfect continuous is formed by using the auxiliary had been+ing form of the verb ( had been working ) .
AFFIRMATIVE : I/you/he/she/it/we/they had been working .
NEGATIVE :I/you/he/she/it/we/they had not( hadn’t) been working.
INTERROGATIVE :Had I/you/he/she/it/we/they been working ?
When do we use Past Perfect Continuous ?
We use Past Perfect Continuous to talk about the duration of an activity up to a point in the past .
I had been doing my homeworks the night before and I was tired.
We use the Present Perfect Continuous to talk about how long an activity had been going on up to the present .
Example. I have been working here for three months. ( I am still working here now .)
We use the Past Perfect Continuous to talk about the duration of an activity up to a point in the past .
Example . When I left my last job , I had been working there for four years. ( I started in 1990 and I left in 1994 ).