How often do we respond to a question or enquiry with 'I don’t know'? How does it feel when you say ‘I don’t know’? What unconscious expectations may be associated with it?
'I don’t know', may have various meanings.
Indecisiveness - when we are struggling to decide about something important be it about work, making a choice, a relationship - the 'I don’t know' can simply be another way of saying that you are not ready to know, and a sense of uncertainty or risk creates a feeling of ambivalence and hesitancy. All you may know in the moment is that you genuinely don’t know.
'I don’t know' - could express a fear of being wrong. Under pressure to give the right answer it might be associated with embarrassment, fear of ridicule and diminishing self-worth.
'I don’t know' - as a dismissive statement might be in response to wishing to avoid difficult situations.
'I don’t know' - may also be a way of saying that you do not have the words to express your feelings or emotions.
'I don’t know' - could express not being in touch with your feelings and emotions.
'I don’t know' - may be an indicator that you are experiencing a range of different feelings and feel confused or conflicted.

Any of these may suggest that you find it difficult to process your feelings and emotions.

I don’t know’ is ‘not knowing’. In therapy, curiosity is an encounter with what we do not know. Through the collaborative work between therapist and client, both strive to be open and tolerate ‘ not-knowing’ or ‘I don’t know’.
'Knowing what one doesn’t know – the known unknown - is at least as important as to know what one does know – the known known'. (Bob Chisholm ‘ The Wisdom of Not-Knowing’)

The Johari Window is a technique to help individuals make sense of the unknown areas of themselves in relation to others and to different parts of ‘self’:
Open Self: What you know about yourself and are also known by others
Blind Spot: What is unknown about yourself but is known by others
Hidden Self: What you know about yourself that others do not know
Unknown Self: What is unknown by you and is also unknown by others.

According to Daniel Siegel ('The Mindful Therapist'), the ‘unknown’ is an integral part of the psychotherapeutic encounter, which brings us face to face with uncertainty. “… sometimes the most powerful statement we can make is an authentic 'I don’t know' or “I’m not sure'.

If you are new to counselling, you may feel confused by uncertain feelings, thoughts or questions that arise. It is in these moments that the therapist’s role is to remain curious and open to explore with you the underlying issues of ‘I don’t know’.