Average weight, 64 yo Caucasian woman. Woke up this morning shaking, could not get warm, fever was 103.5 orally. Took Tylenol a muscle relaxant and after a little over a half hour , fever was 100.5 and I was soakimng wet head to toe. Slept a couple of hours and woke up with fever again and went thru the same routine. No N&V, diarrhea etc but a bad headache all day, I feel like I have been beaten with a stick, any thoughts? Flu and pneumonia shots last fall.