Why do I feel warm and sluggish?

Last night I went to the emergency room because I felt sluggish and my body temperature was extra warm. The palms of my hands were literally on fire as I drove to the emergency room. Along with a horrible headache, the back of my thighs were also sore. The doctors concluded that nothing was wrong with me but I know they are wrong. I'm sleepy every three hours and my body continues to feel sluggish. Point blank, my body is simply tired. I didn't feel this way a week ago and I'm really starting to become scared. I don't know what to do.