I was fine all day yesterday but when I went to bed last night, I was shivering even though it was very warm in the room (according to other people in the room). Throughout the night I developed a very high fever and my whole body was really really warm. I got up in the middle of the night to go to the bathroom and get water, and could barely walk because I felt so weak. I couldn't pick up the water pitcher with one hand because my muscles were so weak, and I could barely grip on to anything. I slept for about 12 hours, and now my fever is mostly gone but my entire body still aches. What do you think this is?