I'm not sure what's the difference between counselling and psychotherapy. The term "counselling" is used only, I believe, in the Anglo-Saxon world; everybody else calls that thing psychotherapy.

But that's not my main question. I wonder how people communicate to their therapists what is wrong / feels wrong/ awkward with them in social situations. The therapist cannot see you in those situations, and you may have a lot of wrong/harmful/awkward reactions which you are not even aware of, so you cannot communicate them. Unfortunately, I cannot stand out of myself and analyse myself from the outside; I'm not that dissociative.

I believe that was my issue in my therapy. How can I communicate with my therapist, if I have issues communicating/being open in general?

I need to prepare for my therapy / counselling, which will hopefully start soon.