What Causes Shivering, High Fever Followed By Headache?

Yesterday, I had shivers early evening that last till bedtime, took a hot shower, then high fever of 102 over night, sweated all night with mild headache, then it all went away the next morning. I took a couple Tylenol before bed. I'm a 34 female, 5'1", 100lbs, always been active and healthy, balance diet. I had sinus infection few weeks ago and doctor gave me 10-day antibiotic. What could that possibly be that I had yesterday/last night?