Is this a sinus infection or something worse?

The doctor told me its a sinus infection but I get those all the time and this is different. I've had a fever of 102-103 degrees f for five days, a super congested nose, but not really the facial pressure of a severe sinus infection, no coughing or sneezing, mild sore throat, severe sensations of hot and cold ( by that I mean I'll either be freezing cold and violently shivering under winter clothes and several down comforters, or I'll basically get hotflashes and sweat like a pig even in an ice cold shower), muscle aches, and really bad headaches. By the way, it's not the flu or mono, doc went over this. I've had both and this is nothing like that.