Clunking noise in rear of 2001 Toyota Echo

Within the past month my car has started making a strange clunking in the rear of the car whenever I back up or when I go forward (at low speeds). I have had the brakes checked,tire lugnuts checked, and new shocks put on, but the clunking is still present. What are some other possibilities of the source of the clunking?? I am going to get the rear struts looked at soon too…