Welcome to HCM
You are having fever
with evening rise for more than 15 days and as you have done reports which are normal, Antibiotics works if there is infection and we can detect where is the infection.
There are many Atypical infection
like Tuberculosis? and sometimes infection may be detected only on repeat examination or investigation.Some times case of drug resistance
would be there ?
There could be a case of PUO ( Pyrexia of Unknown Origin) which requires hospitlization and proper examination and special investigations to know the cause of fever.
Best would be get hospitalize under supervision of Physician and hope your cause of fever will be detected and treated.
Good Luck to you