Sounds like a dream fortelling death by submission under a draining force. Ergo, you're in danger of being hurt by someone who wants to drain the life from you.
you have a war raging inside of you. the vampires represent conflicts you have with others and/ or yourself. the sheet represents you hiding your heart from your conflicts and fears. the blackness is your negative emotions. the dream is telling you to be happy and at peace with yourself you need to face and resolve these conflicts. in other words. kill them vampires.