Can't Wake Up From One Certain Dream !!

I keep having these dreams where i know that i'm dreaming and it's a very scary dream. The problem is that I can't wake up from this dream! It's like something is holding me down and holding my eyes shut so i cant wake up. I can feel myself jerking and trying to yell for my grandmother, who I live with, but I just can't wake up until it wants me to. It's so scary. It feels like something is taking over me. Please help me figure this out. What does this mean and how can i stop it?