How can you tell what a high fever is caused by without going to the doctor?

I had a really high fever last night, not sure how high but i was burning up pretty bad. At first i started getting cold, then after a little while i was freezing, took a hot shower, was still freezing, and went to bed under 4 blankets. I was so cold but my face and head were burning up bad. then i finally fell asleep and woke up 3 hrs later and wasnt cold but really really hot, but i wasnt sweating at all! eventually after a few hrs, i started feeling better and the fever went away. Does anyone know what coulda caused this?? it scared the **** outta me. i feel fine 2day but does anyone know if it wll come back?? Im open to ANY ideas or suggestions. Thank you all so much!