High Fever. Is there any thing to worry.

Hi Iam asking this question on behalf of my brother. My brother was admitted to hospital on 6/10/16 post complaint of fever since 20 days,weakness ,headache and uneasiness. He was negative for Dengue , antibody , malarial parasite , widal titter was normal , CRP-23 and ESR-35. 2 D Echo done was normal.Abdomen showed mild Hepatospenomegaly. Chest X ray was normal. He was started on IV Cetil and antipyretic and IV fluid.His fever was continous though. After 3 days Injection amikacin and doxy was started.Still he was having high fever.Whole body PET scan advised and done on 11/10/16 which showed enlarged cervical and axillary lymph node.Doctors suggested fnac but since his fever resolved since 12/10/16 , hence we didnot go for fnac He was bit stable after that and hence was discharged. Just wanted to know since the temp has come down to 95, 96 , 97 now a days but the patient still has weakness , chest pain and pain just behind the ears....is there any thing to worry.?