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The problems you are describing are related to mental status of a person and do not have any disease in brain so there is no need to investigate your brain.The mental problems can be as a result of mental stress;personality disorders like even inferiority complex;and such problems need counselling
and in few cases treatment.Please consult a psychologist/psychiartrist for help and counselling.Presently your symptoms of allergic rhinitis
will recover after treatment then you can consult a psychiatrist
and you should be fine.