Seeing things at night?

I've only just started experiencing that I might have some sort of spirit following me, it mostly occurs at night but I have seen it at day, last night I was asleep with my leg out of the covers but I felt something touch my leg, so I put my leg back in the quilt and sat up a bit to sleep, later through the night I felt something grasp my neck as if it was strangling me, I actually couldn't breath and when I woke up I saw this white figure like old man stare at me then go, I worryingly carried on sleeping but it kept looking at me across the room, sometimes right next to me, I tried throwing a bottle at it and it just got angry and went, nothing else happened that night but earlier today something weird happened, I was around town with my girlfriend(Who has Schizophrenia and sometimes here these voices in her head as part of the symptoms of it) and as she was going through one of these moments she walked away from me and just at that moment I saw the same figure I saw the night before but right behind her, she was looking at it like she knew it, like these voices told her to, I don't know if anythings connected but I saw it again tonight as I went to the bathroom and saw a quick glance of it in the mirror, I don't know if anyone can help or recommend anything but if you can that would be great, I'm 14 years old by the way so I thought it was a bit weird for this to be happening.