Your description gives me the impression that you are having a fever of unknown origin which will have to be investigated by a primary care
physician. Given the wide range of causes that exist of hyperthermia
it will be wise to start running tests to detect infection. If blood work tests for infection come out clear, then your doctor will probably start testing for other possible sources of the fever. Hormonal
diseases, tumors, chronic infection (TB, viral infect such as HIV etc) will each need to be ruled out one after another depending on the context in which you are in i.e environmental, family history, past medical history etc. Your doctor is better placed to evaluate and get the most probable cause.
If at his level that can be done, then a specialist consultation with an internist is advised.
Hope this helps