I had this a lot as a kid when walking alone or home alone. I wanna chalk it up to general anxiety/paranoia and how your brain decides to manifest that.

You don’t have to answer here but consider your life. Did you grow up feeling unsafe? Do you have general anxiety and has it gotten worse as of late? Any increase in stress?

Something that helped me is owning my space, comforting the thoughts head on. Feel like someone is in your house? Call out and stomp around searching. Tell yourself out loud there is nothing there or perhaps play the TV/music and fill space with sound.

Last idea, get a cat or dog. They’ll notice if someone is around.