The Past Perfect Continuous

      Here's how to make the past perfect continuous. It's 'had' + been (the past participle of 'be')+ verb-ing

Firstly, let's look at the positive form:

I had been living

You had been going

She had been sleeping

He had been working

It had been raining

We had been studying

They had been cooking

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.
Here's an exercise about the past perfect continuous positive form.
Next, the negative form:

• I had not been trying (I hadn't been..)
• You had not been working (you hadn't been..)
• She had not been crying (she hadn't been..)
• He had not been shopping (he hadn't been..)
• It had not been snowing (it hadn't been..)
• We had not been reading (we hadn't been..)
• They had not been running (they hadn't been..)

Here's an exercise about the negative
It's pretty easy to make the question too.
'Yes / no' questions:

• Had I been working?
• Had you been sleeping?
• Had she been reading?
• Had he been watching TV?
• Had it been raining?
• Had we been drinking?
• Had they been eating?

'Wh' questions:

• Where had I been working?
• How long had you been sleeping?
• What had she been reading?
• How long had he been watching TV?
• How long had it been raining?
• What had we been drinking?
• Why had they been eating?

How to Use the Past Perfect Continuous

 How to MAKE this tense.

The past perfect continuous isn't the most common tense, but it's still useful to know.

1. Something that started in the past and continued up to another action or event (tells us 'how long')
   She had been working at that company for a year when she met James. (This tells us how long something had continued before another event in the past. We usually use 'for' or 'since' in the same way as we do with the present perfect continuous)
2. Cause of something in the past
   The pavement was wet, it had been raining. (It was raining before the time I'm describing in the past. We could see the result of the rain - compare with the present perfect continuous)