What Causes Vomiting And Fever While On Amoxicillin For Sore Throat?

Hi. I am an 18 year old, white, female. I have had a severe sore throat for about 5 days now. Both tonsils are inflamed but the left way is by far more severe. I went to the doctor on tuesday, and tested negative for strep. The doctor put me on amoxicillin. Last night (day 3 of antibiotics) I got a fever of 101.3 F. (I hadn't had a fever until then) and then this morning I have begun vomiting. help?