Final answer:
The DSM-5 diagnosis that fits someone who fears having a serious illness despite negative medical tests is Illness anxiety disorder (c). It involves excessive worry and preoccupation with the belief of having a serious disease, which persists even after medical reassurance.
Step-by-step explanation:
The DSM-5 diagnosis that might be typical for someone making the comments "Doctor, I know I have a terrible disease and you just aren't telling me. I do not believe you when you say everything checked out okay" is c) Illness anxiety disorder. This condition is characterized by excessive worry about having a serious illness despite having few or no symptoms and having negative medical tests. Those with illness anxiety disorder have a preoccupation with the belief that they have, or are in danger of developing, a serious disease. This concern persists despite reassurance and a lack of diagnostic findings to support their concerns.
Anxiety disorders are the most common mental disorders in the United States, and it's important to differentiate between normal feelings of anxiety and a true anxiety disorder. The DSM-5 is a critical tool used by clinicians to diagnose psychological disorders, and it provides specific criteria that need to be met for a diagnosis of Illness anxiety disorder.