yesterday when i woke up i didnt feel right at all. all day i felt nauseous and tired and lethargic. then towards the night i started to feel really cold. i took my temperture and it read 100.3. i attempted to sweat it out but that did not work. upon awakening today i still had a slight fever and a pounding headache, which i also had yesterday. i decided to take 2 tylonol and then take a short nap. when i woke up my headache was gone and i took my temperture again and it read 96.5. why would my temp be so low??? i still feel really weak and lightheaded and almost as if my head is in a fog. is this just a cold or the flu? is it something i should be seriously worried about?