The first and most common sign of having a fever is feeling feverish or hot. In some cases, you may feel feverish but not experience running temperature. Preexisting medical conditions such as hormone changes and lifestyle may be responsible for these feelings.
Experts say feeling feverish might not be a serious condition but having feelings of fever without an increase in body temperature could imply the presence of an undiagnosed medical condition. An internal fever happens when you feel very hot but the thermometer shows normal temperature. You may experience symptoms similar to a fever (such as general malaise, chills and cold sweats). However, the thermometer is still at 36 to 37°C which is the normal range.
An internal fever is not a medical condition. It is a way of saying you have the same manifestations as a normal fever without a measurable rise in temperatures. The centers for disease control and prevention (CDC) advise people to measure their temperature frequently if they are not using fever-reducing drugs such as ibuprofen or acetaminophen (tylenol). 
What Does Fever Mean
A fever is referred to as the body temperature that is higher than normal. The normal body temperature is 98.6 degrees Fahrenheit. But some people may have it a bit lower or higher. Increase in body temperature is a common sign that your body is fighting an infection. It might feel painful, but it is a vital technique for your body to fight off viruses and bacterial. Fever can also be a sign of a preexisting condition.