What Causes Nausea And Headache When Suffering From Tonsillitis?

Hi 3-4 weeks ago I had swollen, pus covered tonsils, I didnt go to the doctors but I had a dentist appointment whilst I had this and the dentist confirmed Tonsilitus, Its been my fourth case this year. But since this last time, the pus has cleared and the swelling has reduced slightly, but they still took and feel swollen, so much so that I feel constantly on the point of gagging and my throat feels like its closing, I ve been nauseous for over a week, and over the last couple of days a I ve developed a headache and fever. My tonsils have stayed red since the pus went and a blue vein has become prominent on one of my tonsils as well as several across the back of my throat.