"have been" is present perfect: you understand its meaning correctly.
"had been" is past perfect: don't use it unless you really really need to.
You need to use past perfect if you want to talk about an event (1) that happened before some other event (2), normally one that is described in the same sentence.
When I met John last week, he told me that he had been doing a lot of overtime.
Looking at this sentence, Event 1 is "he was doing a lot of overtime" and event 2 is "I met John". The use of the past perfect for event 1 "he had been doing a lot of overtime" tells us that it occurred before event 2.
here is some more information about past perfect.