Answer:
Insomnia
Explanation:
Insomnia is a sleeping disorder in which a person having trouble falling asleep or having trouble staying asleep. This condition varies according to the patient's condition. It can be for a long time or short periods. It is a chronic condition. It occurs three nights a week.
Insomnia is many types
Primary insomnia
Secondary insomnia
Insomnia have may reason to occur. Thus here Oliver is suffering from insomnia because of exam stress.