What's in my house?

The other day my cousins came over and we played modern warfare and some grand theft auto IV, but after they left me and my sister went to bed. I woke up later that night, I swear on everything that I live for I felt something, I'm not trolling or acting stupid, I really don't know what it is or if somethings in my house, anyways I didn't just feel something, I could see a shadow like see through but the outline and the sides were lit up so I know something was there, my sister said she had seen something last the other night too. I only want to know a little more about it before I tell my mom, and she thinks were crazy.