I have had diarrhoea for nearly 5 days with no other symptoms except sore throat on day 1 and blowing my nose. no stomach pain. could it be a virus?

Sounds like it could: be a viral infection, like viral gastroenteritis which involves diarrhea, upper respiratory infection symptoms, abdominal pain, and/or nausea/ vomiting. Drink three times the amount of liquids (water, Gatorade, Pedialyte, juice, Ginger ale but no soft drinks or alcohol) you normally do to make up for the amount you lose through diarrhea, and go see a healthcare provider if you need nausea control