What Causes Fever Along With Fatigue And Muscle Ache?

I have recently been sick with a fever, fatigue, joint and muscle pain, and other symptoms for several weeks, I just had my urine tested and preliminary results show a high white blood cell count level, I have symptoms related to a bladder| Ute infection and just finished a seven day course treatment of an antibiotic, Although it helped relieve some of my symptoms, I,m still running a fever every day, Next week I will have my blood tested; not sure yet what tests my doctor will order, Close to 3 months ago I had a Total right knee replacement surgery; and a previous pelvic surgery 3 months before that, My blood was tested 9 days after I returned home from my knee surgery and the results showed an elevated level of my white blood count along with slight anemia, This was attributed to post surgery symptoms, Any feedback or opinion as to what may be the cause of my ongoing illness would be greatly appreciated, dlmwpoet4music@gmail,com