I need help with a spirit/demon?

I would get in contact with a local paranormal (or ghost hunters) group and talk to them. Maybe see if they can do an investigation. Most groups, if they're legit and really wanting to help people they will do this for free. Until then, if it's bothering you I'd try to set some ground rules with it such as telling it that this is your home and it needs to leave you alone. Some people put sage in their homes or burn it through a smudging process and supposedly that helps.