Why are these things happening in my house?

Webcams are very cheap and you can set them up with motion detection and voila, you will have some of this on film. If it's all really going on and you are correct in uming no one is physically there, it may well be lower astral entities or "ghosts". Filming may actually not only give you some validation but help your fear levels. And if you do discover that it's entity activity you can get some advice on clearing it.