Hello, First of all I would like you to relax and be calm with the assurance that you are not going crazy. There is nothing to be afraid of. I think you are facing the problem of Obssesive-compulsive disorder (OCD) in which an idea/impulse intrudes itself persistently and impelling into the person s conscious awareness. Obsessions or compulsions are undesired, unacceptable and uncontrollable, the person recognizes obsessions and compulsions to be absurd and irrational and feels a strong need to resist them. Musical obsessions are those in which patients experience repetitive phrases, tunes or complex musical pieces that originate inside the head. These are less common symptom of OCD. You need to start with some anti-obsessional medications like Fluoxetine. Your problem will resilve but it will take some time. Try to divert your mind whenever the particular song originates in your mind instead of trying to repeatedly stop that song. Hope this helps you. Thanks.