Phobia

I'm sleeping alone in my room for the last two months, but before that I used to sleep with my mother or my grandmother, then I read a lot of ghost story books with bravery at night, then I was not afraid but after that , I have been staying alone for study at night in my room for last two months. For last week I finished reading a ghost story book. After reading that ghost story book I can't sleep alone in my room at nights. I feel me safe when anyone (my mother or grandma) is staying with me for whole night. but when l'm alone, when I close my eyes, I'm thinking that there is someone or any ghost is near me and see me. I can't sleep alone then. This phobia is disturbing in my normal study and health life. How can I get rid of it?