Chills on&off, nausea, severe headache, occasional diarrhea & no fever for a week & now starting having a slight fever. any idea?

Likely Viral: Your symptoms can either be viral or bacterial. The headache, new fever, diarrhea lean toward viral. Go see your family doctor for an evaluation. You might have an ear infection or pharangitis.

Difficult: I would get seen. It sounds viral, likely, but the time course is long. Check a upt and check your temp, subjective fever is common? R u sleeping at night? Clinch or grind your teeth at night? That's a wide list but the duration, headaches and fever point to needing an appt.