Dear Patient: Blood cancer will not present with continous coughing,instead a lung cancer does so.
But yes, loss of weight more than 10% of his previous weight,is one of the symptom of cancer.
Immunity disorders do present with increased rate of infections,auto immune disorders,which are different from cancers.
Blood cancer persents with increased bleeding,immuno suppresive conditions hepatomegaly,spleenomegaly,lymph node enlargement.
Either he could be suffering with a blood cancer ,meet a haematologist to rule it out,or he could be suffering with a hypochondriac disorder,for which he needs to consult a psychiatrist.
Hypochondriac disorder is a condition where the patient will be assuming that he is suffering with many diseases ,which he actually will not be suffering with.