To dream of being stabbed in the back shows that you are aware that there is an underhanded or dishonest act taking place in your life. You are being taken for a ride and you don't like it. Open your eyes to the situation and make moves to bring your feelings into the open.
Dreaming that you are stabbing somebody in the back suggests that you are behaving badly. You need to find a way to be more honest in your life as any harm you do to others is harm you are ultimately bringing on yourself.