20 M: What am I doing wrong?

I've never had an in-person relationship. I've always and still am the 'nice guy', who does a lot for everyone and is always selfless and hardworking. Yet, I feel invisible. I feel like no one wants me? I went on Am I Ugly, and people said I was fine, so what am I doing wrong? Am I in some sort of a limbo? I feel like sometimes I just want to eat a shotgun shell for breakfast and call it a day. I am tired of being lonely, when everyone around me is in a relationship and happy.