Hi. My 12 Year Old Son Has Had A Migraine,

Hi. My 12 year old son has had a migraine, stomach pain without nausea, and a fever between 100° - 103° for two days. Pediatrician dx sinusitis and Rx Amoxicillin. Temperature suddenly dropped to 97 about 3 p.m. and not increased to regular temperature even after attempts to warm up. About .5 hr ago began sweating profusely in legs and temp dropped further to 96.4. Please help!