Thanks for posting you query to health care magic.
there are many reason for fever and the investigation you have undergone didn't detect all cause s for fever so you need to undergo some more investigation but before that you have to tell me some more clinical information so that i can suggest you supportive investigation .
1.is fever associated with either cough ,
weight loss ,
diarrhoea, joint pain, body rash , loss of appetite,
ear discharge, sinus discharge, cold.
2.is fever come at definite time like at night or morning or after a definite intervel .
3. which antibiotic you have taken .
as antibiotic are not helpful if your infection is due to some parasitic cause like
malaria, bebesiosi or due to some bacteria like
Mycobacteria .
allegra D is antiallergic medicine not helpful in treating infective cause . Send me detail as soon as possible so taht i can manage your case perefectly .
hope you are satisfied with my answer . feel free to communicate if any query .
regards,
Dr.Manish Purohit
Infectious disease specialist