Spirits/Ghosts in my home?

Since we moved into our home last July we have had several things go on that indicate there is something "non human" here. My sons bedroom is off the living room and several times when watching tv at night I had seen a shadow that looks human coming out of my sons room and around the corner into the dining room. One night my mother in law was visiting and I saw "the shadow" and my mother in law also looked up and asked "who's your friend"? She had also seen it. Since then my partner and brother in law has also seen it. My son has never complained about anything funny going on in his room but one night when his 3 year old sister fell asleep on his top bunk she woke telling me there was something in the closet. In the last few months my 3 year old has been waking up in the night crying (something out of character for her) saying she thinks there is something in the room. She also has started to refuse to walk through the dark rooms to get to the toilet (even though the toilet light in on) which is something that never used to bother her. Today my 6 year old girl (who shares a room with the 3 year old) says that she woke during the night and thought someone was spying on her. She said she could see a face at her door watching her and after she closed her eyes and re opened them it was gone. This is the first thing I have heard from her about it so its making me more concerned almost like whatever it is, is getting braver. My partner mentioned that he was once in the toilet (which is off the laundry) and the laundry door has shut itself. This has happened to me before as well. Once a top closet door by the laundry also flew off onto the floor. What can I do to find out what is going on and how do I stop it? Whats the deal with home blessings and things as such? We are not very religious people. Please help. Thanks in advance.