Fever continues from 20 days. The cause?

I had fever on 10 feb, then take medicine and was allright. Then again I have got fever on 19 night and it was 102°F and again I consult doctor. He prescribed medicined and I had taken them. The fever continues at around 100°F to 101°F. (Sometimes more than that). Again I moved to doctor, he prescribed some tests follows: Typhidot Igm - Negative Blood Culture - Negative CBC - Normal, Fever still continues at 101 °F and less. He prescribed Taxim-O and Calpol 500. Fever ends for 3 days and after 3 days, it still continues at same temperature. I switched to another doctor (since mine is on leave). He make tests for: Thyroid (T3, T4 & TSH)- Normal C reactive protein - positive - 43mg/L Hepatic Profile (LFT)- bilurubin (total) 1.5, Bilurubin (direct)-0.23mg/dL; ALT SGPT 79 IU/L Doctor prescribes Dolo 650 and Pantocid before test report view. When I take paracitamol, fever resides and again after 5 to 6 hour, it starts propagating at temperatures of about 100° and 101°. What is the cause?