What Causes Confusion In An Elderly Woman?

my 85 year old mother is having trouble with confusion especially at night.. She is insisting this is not her house nor her bedroom, she is refusing to go to bed. I have showed her pictures of her any my father on the wall etc. she said there all over this place but this is not her house. She fell and broke her tail bone in May she was in the hospital for 3 weeks then went to a nursing home was ther for a week and was acidentally overdosed with dilotted and had asperated phnomia. she was taken back to hospital by aid car then went to different nursing facility for 2 months physical therapy. She can not be alone so I moved in with her when she was released Aug 31st the confusion is steadly getting worse. Her Dr tested her about 3 weeks ago for Dementia or Alzheimers and said she does not have either one. Something is going on I don t know what to do she get so angry