Dear Ann,
EMDR is not a "truth serum." There is no such thing. When images come up in therapy--EMDR or any other--there is no way of knowing if they are historically true or not without present/physical verification. Sometimes "memories" are stored in fragments, or distorted pictures, or vicarious traumatization from movies, stories, dreams, lies we have been told, images that represent rage/shame or guilt, etc. As another example, most people remember that when they were young - at times they were not sure if something actually happened or if they had dreamed it. If those images came up during therapy there would be no way of knowing in the present time either.
Try not to be concerned about the truth of any of the images. There is no way to be certain about them without present corroboration. The important goal is to deal with the symptoms and their present negative effect on your quality of life. Just concentrate on the healing process.