Seeing things that aren't there

I'm Shea and I'm 17 and I've recently for the past five weeks been seeing strange things , first I just saw them out the corner of my eye then I saw shadowy figures or animals that weren't realy there and now at night I dream about these things with gaping mouths no eyes and claws. They are chasing me and telling me to do Hurt my self or kill my self but when I wake up there faces are jumping out the dark at me and I can't sleep anymore , and starting last week I can't be alone cuz I feel something watching me waiting to do something , can someone anyone tell me what's going on PLEASE !!!! The last time this happend I was 8, and 13