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This is a chronic fever, which is called as pyrexia of unknown origin when we are unable to ascertain a cause.
As your blood tests and x-ray are normal, lung infection is ruled out.
Conditions causing chronic fever are numerous. Also, certain infections like tuberculosis, HIV and malignancies can cause it. But, in your case it is unlikely as there is no weight loss or other risk factors, neither you have an x-ray abnormality.
Now, we move to the lymph nodes. Do you have any lymph node swelling? If yes, then get it tested. Try to get an ultrasound of abdomen to rule out lymphadenopathy.
Get a urine routine and culture as sometimes a mild urine infection can get unnoticed and cause fever. Get a blood glucose and renal function test too.
If everything comes normal, then we should look for anemia. A low hemoglobin can cause low grade fever and fatigue.
Fungal infections usually cause severe illness. To confirm if it is a fungal infection, a blood culture is required.
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