In our clinical practice we first rule out the possibility(though not common then Infection) of TB and Lymphoma
as the first cause of night time fever. If i would be treating you i would do a Clinical examination and recomment Complete blood profile and an ultra sound
abdomen for any Lymphnode enlargement, Elisa
for TB, Urine tests and Chest X Ray
. If these causes are ruled out then rest assured that other things are not quite difficult to treat. Now concerning your present scenario of repeated surgery, infection of Urinary tract
cannot be completely neglected as a potential cause for the fever, so i would not like you to worry till the results show up.I wish you good luck and get well soon.
Hope my answer are satisfactory.Any future quarries are welcome.