I Am Lonely

Really, why do I have to be so lonely? Don't have even a single true friend with whom I can share all my feelings with. It's really sad. Sometimes I wonder if I did anything wrong that would make me bad in the eyes of others, but I really can't find anything like that.
I feel jealous seeing others talking, hanging, playing with their friends. Although it's not that people hate me, it's more like they don't like me. Like I am invisible and no one at all is there to be with me. I feel absolutely useless and pathetic. I think that if I would die, no one would notice my absence.