dear user Fever and nausea is indicative of an underlying infection that cause these symptoms.........fever and nausea can be caused by bacterial or viral infection that is should be diagnosed and detected .......common cold or urinary tract infection or may be typhoid, or TB or Dengue. you should do some investigations for that urine analysis and widal test and tuberculin test for investigation may be needed also cbc ,blood culture will be helpful you should see your doctor for examine any abnormalities that you canot detect your self you need not to be stressed about that just see your doctor and discuss with him to do these investigations that detect cause hope that helps you