I have had 2 dreams like this in my life. In my dream, I scream and nothing comes out. The second time this happened I found out that although I did not hear anything in my dream, it was heard by my roommate in the awake world! I woke up with her peaking in my door and asking if I was okay as she sure heard me. Also, both these dreams occurred when I was trying to find a solution to a stressful issue that I had no solution for. Hope this helps.