Need paediatric Dr help urgently!! My baby sick for 7 weeks already still no diagnosis yet!!!?

My baby(one and half year old son) has been sick for 7 weeks until now. I brought him to EMD and he had admitted for 2 weeks for unknown fever. His fever at the first week is 37.6 is max T (Temperature) then 2nd week T max is 37.7(he saw dr and gave amoxicillin for 3 days) and 3rd week T max is 37.9(as the fever didn't go down in 48 Hr of antibiotic, I brought him to EMD and dr changed to augmentin) the fever didn't go down also and he saw his paediatric dr and changed to another antibiotic which is not penicillin group. I gave it for one week and the fever is stll increasing. In 4th week T max is 38.5. He had fever everyday and it never went down to normal. After I noticed T max is 38.5, I brought him to EMD and got admitted. Firstly, dr said mostly likely viral like (EDV). EDV is negative after blood test. Dr also did blood test for autoimmune, antinuclear, SLE, CMV, FBC, LFT, blood culture, urine culture, PBF. Nil chest infection by chest x ray.Noted WBC is 20.45, lymphocyte is high (can't remember), monocytes is 1.4 and LDH is 1226, PBF show lymhpocytosis. Other than that the rest of the blood tests r normal.Because of prolong fever and FBC and LDH abnormal, oncology dr saw my baby. Oncology dr thought that fever may be because of leukaemia according to FBC, LDH and PBF result. Bone marrow aspiration doneand it shows normal. No acute leukaemia. Then dr suggest PET CT scan and flow cytometry to rule out inflammation and tumour inside the body and JMML. PET scan show normal and flowcytometry also normal. After two weeks staying in hospital, WBC, Lymphocyte and monocytes back to normal and he was discharge but he was still having fever at the time of discharge. He didn't has any antibiotic, only parecetamol for fever. The fever used to go up to 37.9 or 38 in the morning ( around 10 to 12) it went down to 37.7 for the whole evening. His fever only came down at night time while he is sleeping (T range from 37.1-37.3).Please help to diagnose for my baby. Thz