I Had Triple Bypass Heart Surgery 4 Yrs Ago. I

I had triple bypass heart surgery 4 yrs ago. I have had low grade fevers ever since. If I am given antibiotics fever goes away. I almost always have symptoms of a sinus infection. Last summer, no fever for 6 months until taking care of sick daughter and newborn baby last October 29, have had low grade fever back. I have had every test done including bone removed from hip to check for cancer . nEgative. The only thing showing up is an elevated IGM test which doctors say is an infection but don't know where it is coming from. Getting to feel hopeless and depressed. Thank You, Elaine