Unexplained fever for last 1 month. Have done all bllod tests, urine, x-rays and ultrasound, nothing came +I've. I had low fever last month, usually came in the evening, and went with muchmedicines after 3 weeks. I was fine for about two weeks. But fever started coming again, and this time high fever100 - 102, and stays full day with a headaches. Please suggest.