I'm pretty sure ghosts exist. This story isn't bullstuff at all, this happened to me about 7 months ago.
So i was laying in my bed, but i couldn't sleep. I kept feeling scared/like something was there. Nothing happened yet though, so i turned on the light and kept trying to go to sleep. I think i could feel that something was present. So i went downstairs into my living room to try to sleep, and i felt a little better, but still couldn't really sleep. This is when stuff got scary: I heard a growl, like a deep dog growl, but it sounded like a human was making it. I got creeped the forget out, so i went into my mom's room, but she wouldn't let me sleep in there, so i slept in the guest room right next to hers. I fell asleep easier that time. So in the middle of the night, i hear a door slam. My mom got up to see what it was, and noticed the it was the bathroom door. She thought it was our roommate, but no one was in there. When she tried to open the door, it was locked from the inside, and she said the doorknob was ice cold. No joke, this actually loving happened and was creepy as stuff.