Social anxiety disorder, you do fear to be in public openly
So you can practice to be in public while you are with your close friend you trust, then... slowly by slowly you can try to do it alone.  more

I feel like I m a lone and when I m that moment I don't feel happy

Thank you.

therapy (especially cognitive behavioral therapy or CBT), medication (antidepressants or benzodiazepines), and self-help techniques