I think it's just me that worries all the time about this.
Is there anything you want to talk through about your fear?
Am I the only person in the world?
As far as I'm aware of you are not the only person in the world. It makes sense that you would worry about that as it's normal to want to be part of a group.
So, I'm not the only one in the world, but I feel like it all the time and it makes me afraid.
I understand your anxiety in feeling that you are not a part of things, but allowing it to take over your thoughts is detrimental to you. Get out and find some like-minded people to spend time with and your anxiety of being alone will slowly fade away.