Ghost Or Imagination?

I’ve been living in this 2 bed room house for nearly 5 months. When I first moved in, there weren’t anything strange in particular about the house and to be honest I felt quite content to be living there. I mean, this house I currently live in is much much better and bigger than the house I lived in before. It’s not scary and by the look of it, the building is fairly recent built, but out of the blue 2 months ago I had this weird and unexplained activities going on. The story goes like this.

It was one beautiful sunny afternoon. The bright ray of sun shined through my window bedroom. The clock on the wall showed that it was 3.15, early in the afternoon.
I was home alone so I parked my bike inside and locked the front door. I was sure nobody was home but me since my roommate was out teaching and the only entry to the house is through the front door, the back door in the kitchen had been pad locked for along time, even before I moved in. Once I was sure that everything was in its place, I then closed the door to my bedroom, turned on my laptop, and then lied in bed watching a movie I downloaded the night before. Half way through the movie I was startled to have heard the door to my room was pushed open as though someone had grabbed the door by the knob and slammed it as forcefully as “he” could. I put my earphone down and jumped to the door but I could see no one. I checked the front door and it was still locked. I went to the kitchen to the padlocked door and there’s no way someone could get through it. I couldn’t come up with any rational explanation. To open the door to my bedroom, you have to hold the door knob and unless you turn the door knob you won’t be able to open it in the first place. It was not a windy day and if it was there’s no way the wind could hold the doorknob, turned it and pushed it open.

Another incident is when I woke up early in the morning to find that a box of books which weigh more than 6 kg moved on its own. Well, I didn’t see it moved, but I woke up one morning and found the box was in different place. I went to investigate and saw that the box was dragged 20 cm away from its first location. The two incidents showed poltergeist activity, ghost or other supernatural being supposedly responsible for physical disturbances such as loud noises and objects moved around or destroyed, and this is the only time in my life I experience things like this. I don’t know what to make of it, should I just shrug them off or should I be looking professional help to get rid of these nuisances?