The present perfect progressive tense has several
different uses. One is to show an action that began
in the past and that is still continuing now. When the
present perfect progressive is used in this way, the
length of the continuing activity is emphasized; this
usage also suggests that the action has continued with
no interruption from its beginning until the present.
The "time words" for and since are common with
this use of the present perfect progressive.

Another use of the present perfect progressive is
without for, since, or any other time expression:

Joe has been studying at State University.

The baby has been crying.

I've been driving.

When the present perfect progressive is used in
this way, it suggests that the activity was happening
(in progress) in the very recent past:

Joe has been studying at State University.
(Joe isn't studying there now, but he was
studying there in the very recent past.)

The baby has been crying. (The baby
isn't crying now, but she / he was
crying in the very recent past.)

I've been driving. (I'm not driving now,
but I was driving in the very recent past.)

Here are some more examples to make this use clearer:

Sara's eyes are very red. Has she
been crying?

Jim seems to be tired all the time.
I think he's been working too hard.

Has Bob been attending his classes?
I haven't seen him on campus for
at least a week.

Susan's car is in the shop, so she's been
taking the bus to work.

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Special Note:

When the present present perfect progressive is used
in this way, the "time words" recently and lately
are common:

Sara has been crying a lot lately. What's wrong?

Jim's very tired because he's been working too hard recently.

Where's Bob? He hasn't been attending his classes lately.

Why has Susan been taking the bus to work recently?
Is there something wrong with her car?