I've been hallucinating lately and I don't know why? Help?

I'm 15, a boy, and healthy. On no medication, I don't smoke, drink, or have smoked weed or anything like that before. But the thing is, I have been hallucinating lately. They are not vivid where I actually go into this lala land its just im seeing things that aren't really there. For instance, when my phone alarm goes off in the morning it creates a dim light and when I turned my head I swore I saw a face just looking at me. And not that long ago I always see my cats running past me in the corner of my eye, but when I turn to check... they are not there. They'll be on the other side of the house, no where near me. When I was a young child I always saw things that weren't there, I remember it so well because the things I thought I saw used to be so scary, like demons.