It's tough to know when someone is honestly listening. I'm not open to discussing thoughts or emotions to people as well, but slowly talking about it does help. Eventually you do find someone willing to listen, and you will find your own personal ways of releasing emotions.
I think I know what you are talking about. I don't want to always really want to be sharing something deep about my feelings with someone who is only asking to be nice. So, When do you think they actually listen, if ever?