Is My Son Seeing Something I Cannot?

This all started about 3 days ago. My 2 year old son awoke from his nap shaking and terrified. (He is very advanced for his age and speaks in full sentences already) Anyway, he told me there were monsters in his room and they were trying to get him. I know, children have overactive imaginations and it could be that. But then that night he awoke again, trembling and telling me the hand was going to get him. I asked him what hand and he said "There was a hand in your clothes and it's going to get me" This really freaked me out. He finally did sleep in his bed all night last night, but when he woke this morning, he refused to come out of his room because he said the hands were going to get him. I told him there are no hands and mommy will protect you. He then slowly walked out of his room, looked at the dryer on his right and ran past it and came to me shaking. He has never done this before.

I have never experienced anything in the house myself, other than the occasional feeling of being watched. This usually only happens when I am alone and sometimes I see what appears to be someone peeking around the corner at me from the top of the stairs. When I am in the upstairs bathroom, I can look left and see the top of the stairs clearly. I do watch a lot of ghost shows lately (Ghost Adventures is my all time favorite) but this happens when I am not even thinking about anything scary. It doesn't really scare me because once I look and don't see anything; I just laugh it off and chalk it up to watching too many ghost shows.

I guess my question is, could my son really be seeing something? Or is it most likely a phase? Like I said, he is only 2. My daughter, who is almost 4, went through the whole "monster in the closet" phase, but quickly got over it when I told her there was no such thing. It worried me at first, as our attic entrance is in her room, but she even tells my son there are no monsters so I believe he heard it from his cousin or another child.

My daughter did start asking him about his dream (the day he awoke from his nap, I asked him if he had a bad dream, that's when he told me yes and that monsters were in his room), so he could be liking the attention he gets from it. I just don't want my son to be so afraid, I mean I have never seen him tremble and cling onto me like he did that day. Him speaking of a hand concerns me. I do not know where that came from.

By the way, I do not let my children watch anything scary. My daughter once saw a preview for a scary movie (Unborn) and I didn't know she saw it until she woke up from a nightmare saying the old lady was trying to eat her. I saw that preview and realized she had seen it. Now I make sure if any scary previews come on, I change the channel quickly. So I know this isn't something he saw on television.

The house is fairly new (about 5 years) and I'm the 3rd person to live there. I do not know anything about the land, however, and it was nothing but woods before they started building my neighborhood.

Any suggestions as to how to determine whether my son is seeing something or going through a phase would be highly appreciated.