Is this normal?

I always seem to think dark thoughts, is it normal ?

For example, when I come home, as I come out of my car I always think there’s someone around to attack me so I rush in my house. Even when I walk to get in the house I’m always stressed, looking around and rushing to get home.

This goes every time I’m alone. I always try to switch my thoughts but I can’t in these situations.

Do you think there’s a reason for this ?

Thank you