Jaundice (skin and corneas turning yellow) is a symptom that can indicate a lot of things. It can be nothing serious like taking too many beta carotene supplements, drinking too much carrot juice, or it can be very serious, like liver cancer. See your doctor.

When that happened to me and my roommate in college it was mononucleosis, which occurs most frequently in teenagers. That's a viral infection that slows you down significantly but there's nothing you do for it but rest and sleep a lot for months.