What kind of illness: strange smell, weakness, not eating, sleeping, no fever?

The past couple days my husband has been in bed sleeping and not eating much at all. He said he doesn't feel sick, and he has no fever, but he can't seem to stay awake. I noticed he is also having weakness when he moves, maybe from not eating. His skin and breath smell like sickness. What could be causing this? Is it a weak form of the flu? Should I wait it out, or should he see a doctor?