I had a fever of 102.2 yesterday even after it died down from medicine and a horrible headache, fast heartbeat, nausea, and a bad sore throat. Why?

Apap inadequate. Pt treated for fever, needs more evaluation flu, vs strep vs other (diphtheria?).
See below. These are symptoms that could be potentially serious. Yous should discuss these with your physician. He/she will thotoughly evaluate you and let you know what's going on.