I feel tired and my head and body feel heavy/sluggish. headache and stomachache as well. feel like its a bad idea to go to uni..

Viral illness?: Is possible here. And the treatment for this would be rest. So perhaps better to not go in. Need to be checked urgently by a doctor if headache or abdominal pain is severe, you are persistently vomiting or breathing is difficult.

Viral illness : Seems like you are having initial symptoms of viral infection. Try paracetamol, rest , drink lots of fluids like soups . If you get any sore throat or rashes or vomiting or light annoys your eyes or anything that worries you then please consult your doctor immediately