hypochondria

/ˌhaɪpəˈkɑndriə/
noun
  1. A condition in which a person is excessively worried about having a serious illness, even when medical tests show they are healthy.
    • His hypochondria made him visit the doctor every time he had a minor headache.
    • People with hypochondria often spend hours researching symptoms online.
    • Therapy can help manage hypochondria by reducing health-related anxiety.