I don't know if this truly happened or it was a mere image of my brain - a hallucination some would call it.

Sometimes I would be in my house and I would see some shadow-like things fly quickly across the room. I would also see them in corners and stuff when it might be dark - it sometimes taking a form of a black blob or a more silhouette of a person. Like I mentioned before, I don't know if they are actually there, or if it's my mind making it up. It makes me really paranoid and makes me think I'm being watched. I would feel uncomfortable afterwards.

The shadow-like things wouldn't be close to me. They would just move at the other side of my room. But the fear and paranoia can also be from my brain too.
This would happen every once and a while and the shadows aren't really dark. They are more like a see-through black if that makes sense.