We can use all these forms:
to talk about the
past:
He
worked at McDonald's. He had worked there since July.
He
was working at McDonald's. He had been working there since July.
to refer to the present or future in hypotheses:
It might be dangerous. Suppose they
got lost.
This use is very common in wishes:
I wish it
wasn't so cold.
and in conditions with
if:
He could get a new job
if he really
tried.
If Jack
was playing, they would probably win.
Past Tenses
Simple
I worked
Continuous
I was working
Perfect
I had worked
Perfect continuous
I had been working