Hypochondriac (noun)

A person who is excessively and unduly worried about having a serious illness.

Origin:

From the greek hypochondria (the region of the abdomen), from hypo- (under) + chondros (cartilage), from the belief that illness in this region caused a person to be a hypochondriac.

Examples:

1. He was a hypochondriac and always thought he had some serious disease.
2. She was a hypochondriac and always went to the doctor with some imaginary ailment.
3. The hypochondriac is always worried about his health and visits the doctor frequently.
4. He was a hypochondriac and always took medicine for imaginary illnesses.
5. She was a hypochondriac and always thought she had some serious disease.