Why have I always felt as though i'm being followed?

Ever since my childhood, i've had an uncomfortable, and nagging feeling that I'm being followed by something. I don't know what it is, but this feeling has continued to reappear with greater intensity as I have gotten older.

Yesterday whilst driving my car I had this thought and wrote it in my notepad.

'I hold myself & others to extremely high standards. Therefore if I don't live up to my own standards or fail to meet my goals, it creates the feeling of being watched, due to the anxiety and shame of feeling like I have failed myself.'

I think I might be onto something, but I still believe the feeling runs deeper, possibly even connected to events in a past/parallel life.

Either way i'm not sure, and would appreciate any opinions or different perspectives on what could be causing this feeling as its very disruptive to my daily life, in one instance (about a week ago) I actually crashed into another vehicle from being distracted by this feeling.