May there have been paranormal activity?

My house is like any other house, but it has a hint of paranormal activity, but nothing to go to extremes about. It started when I was younger that I would feel as if someone was watching me (mainly in the basement where my room is), nd then it grew to the point where I would hear unfamiliar sounds. I heard footsteps just outside my room, so I got up and no one was there. There was a time when I was sleeping, nd my bedroom doorknob started to shake as if someone wanted in (I had it locked, thank god). When I asked who it was, I heard "it's me", clear as day. It sounded like my mother so I opened the door, but found no one there. My mom crushed her pelvis prior to this, so I found it odd that she'd be downstairs anyways. I've had friends tell me they've heard footsteps on the stairs while sleeping (I'm a heavvvy sleeper, so that was new to me), nd my cat who is dead now would stare into the laundry room forever, which is also downstairs. When I leave downstairs, I make sure the cupboard doors are closed, but when I come back, they're open. I've moved out of there now, nd the owner now tells me that the cupboard door did in fact slam shut one of the nights, nd there are but not much ghostly encounters. It's nothing to get all worked up about, but could have there been a ghost, and still is one down in that basement?