Hi Ebbie
It is indeed possible you may have resident or visiting spirit in your house.
Has the unsual activity only just started occuring?
Best thing to do in your situation would be to set up those trigger object/s as described, also I would advise leaving a tape recorder or audio recording device of some nature in an empty undisturbed room with the windows closed, and door shut.. You may be supised at what EVP you pick up. This is generally the most effective way I find to test whether there are spirits present, if they can communicate with us some how, and let us know that they are there - then trust me, they will..
Have you taken any photograph's of your house recently? Especially in the area's where the unusual activity occurs most frequently.. Give this a try, orbs, strange figures, and other unexplained photo anomilies often show up on camera in haunted locations.
Let us know how you go.. Good Luck..
Kurts
Ph. D. Metaphysics