New Ghost In Old House, Different People With Same Experiences

My boyfriend's house was remodeled when he was 5 or 6 and an addition was added that included three bedrooms and a bathroom. He's now 20 and I've been dating him for 2 years. I've always believed in ghosts, because a home that I previously lived in was haunted; my boyfriend does not believe in ghosts and says I'm crazy and laughs at me for believing (very annoying). Last night, his younger brother (18) and his girlfriend (22) told me they had experienced odd things in the house. I have experienced odd things too, and did not tell anyone about it (I thought I was crazy, since I experienced these things in the "new" part of the house). These are the experiences that we each encountered:

On SEVERAL occasions, I've been in my boyfriend's room alone (day or night) and I've heard footsteps in the hallway (like boots). Everyone else is either not home/outside or its nighttime and everyone else is asleep. It sounds like someone walks down the hall and kind of stands there for a minute and then walks away. Other times, this will have happened and then the door will open or try to open (if it's locked it doesn't open). And yet, other times, I'll hear the door open and I'll look to see who it is and there will be no one, but the door will be open (when I know I closed it). So, I don't pay any attention to these things since they aren't REALLY scary (just a little creepy) and it's in the new part of the house, so I've thought 'No... It can't be a ghost; this is a new part of the house.'

Another thing that has happened a couple of times is I've been there alone (or thought I was at first) and I will hear what sounds like a four wheeler outside of the house in the side yard. It sounds like someone showing off and revving it up or doing doughnuts or something. I looked out the window and saw nothing. I thought maybe my boyfriend's brother was home and I didn't know it and he was riding my boyfriend's 4wheeler and that by the time I looked out the window, he had taken off somewhere else where I couldn't see/hear him anymore. So, once my boyfriend got home (like, 10 minutes later), I asked him if his brother had borrowed his 4wheeler and he said 'No, I have the key in my pocket.' I didn't tell him why I asked because I know he won't believe me. So later, when I saw his brother, I asked him if he and his friends had been riding around the house that day and he said 'No, I've been at work all day.' Another time I heard the 4wheeler was at night and my boyfriend was at work and his parents were asleep and his brother was out (by this time, his brother had bought his own 4wheeler). When he (the brother) got home I said, 'You shouldn't be out there tearing up the yard like that while your parents are trying to sleep. Who where you showing off for?' (I assumed he had brought someone over to show them his new 4wheeler) He said, 'What are you talking about? My 4wheeler is broke and I just got here.' The sound is too close to the house to be someone on the road and all of their neighbors are elderly and don't have 4wheeler/motorcycles/dirt bikes, ect...

So, last night, my boyfriend's brother and his g/f came to me and told me about things that happened to them (I never told anyone what I experienced) his girlfriend said that one day when she was at their home alone and she was sitting in his bedroom (my boyfriend's brother's room) reading and she heard footsteps coming down the hallway (like boots) and she thought that maybe my boyfriend hadn't left for work yet or that their dad had come home for lunch, so she didn't really pay any attention to it. Then the door clicked and swung open by itself. So she got up and left the room and walked around the house to make sure no one had broken in or anything. She didn't tell anyone about it and brushed it off as a draft and her imagination.

A couple nights after this happened to her, her boyfriend called her and woke her up at 4am and told her that strange things were happening in his room. On this night, he was sleeping (me and my boyfriend were staying at my house) and he heard what he described as a motorcycle revving up and driving by his window. It woke him up, and he looked out the window to see what it was and there was nothing there: not lights, no cars, and nothing on the road either (you can see pretty far down the road either way from their house). He thought maybe it was a dream, so he lay back down in his bed to go back to sleep. Before he fell back asleep, he heard footstep (like boots) in the hallway. He grabbed his phone and looked at the time (he thought it was his dad going to work) and saw that it was only 3am (his dad doesn't leave until 5am). So he thought that his dad was going to work early or something, but he got up went into his parents room. He woke his mom up and asked if his dad had left for work yet. She said "No, he's sleeping right here." Then he asked if they had heard the footsteps. She said no and woke up his dad to go check the house and make sure no one had broke in. So he and his dad went and looked throughout the house and didn't find anyone, so they went back to bed. He made sure to pull his door closed until it clicked. He got in bed and had his back turned to the door and he heard his door click open and it creaked open. When he tried to turn to see what it was, he couldn't move... Not out of fright, but literally, could not move because something was putting pressure on his back so that he could not turn over. He stopped resisting and just lay there a few minutes, then when he tried again, he could and he turned the TV on and saw that the door was pushed wide open. That's when he called his girlfriend to tell her about it and she told him that she had similar experiences.

Once they told me about it, I told them about my experiences and it all kind of clicked. He remembered me asking him about the 4wheeler on the two occasions that I heard it, so he immediately believed me.

I don't understand how, if this is a ghost, it can make noises and move/touch things. How it can make sounds when there is nothing actually there? How can we hear foot steps when there are no boots to be making this noise? How do we both hear an engine revving, when there is no physical motor? How can a ghost move things like the door or touch people if it doesn't have a body? Why would it hold him down like that? And where is it coming from? That part of the house has a basement as well. When we told his mom about these things, I suggested perhaps there was a grave under the new addition, but she said they didn't find any bones/graves when they dug out the basement. And she said that she has been having a reoccurring dream for a while. In the dream, she lives in a house that is haunted and she goes around telling the ghosts to leave. She said the other morning she was walking into the bathroom (on the old side) and she heard a girl's laughter (when neither of the girlfriends of her sons were over... Actually, no one was home)...I'm just really confused about all this and now that I know I'm not just imagining it and other people are experiencing the same thing, it's kind of freaking me out! My boyfriend says we are all crazy and doesn't believe in ghosts. His biggest thing about our stories is that he's lived there his whole life, and they've never had anything like that happen, so why would it start now? And how can we hear things and feel things that aren't actually there? If you have any ideas about what could be going on, please share!