two days

[azz]

What does;
"He was two days dying."
mean?

a. He took two days to die.
or
b. He had been dying for two days at the time we're speaking of. (Maybe he died days later.)

Is this form used often?

I was two days working at my new job.

[Tdol]

It means 'it took him two days to die'. It's not that common, IMO, but you will hear it used, certainly in British English.