Suggest Treatment For Severe Chest Cold And Cough

I had a severe chest cold and went to the doctor on Friday. She gave me an antibiotic and cough meds. I was feeling much much better over the weekend and worked all day Monday without incident. When I got home Monday night I got very very cold. I put three layers of clothes on but I was still so cold my teeth were chattering. My skin got very sensitive and so I took my temp which read 99.8. My temp normally run 97 to 98.1 range. Fever finally broke at 4 am Tuesday. Since then I have felt so drained and zapped of all energy. Why would I get a fever after three full doses of antibiotics? I hadn't had a fever since I had mono 18 years ago