Still sounds like you just lose control of the dream. Next time you feel like you are watching it, try to put yourself back in it by moving your awareness into the dream you are watching. Think of it like a WILD sort of. Put your awareness of touch, smell, feeling, sight, all of that, literally into the dream as you feel it fading. If it fades too quick, then simply allow it to fade but remain completely still and re imagine a dream, and you will re-renter one within seconds.