Try the Sports Medicine clinic at CGH. Can get subsidised rates if referred by a government polyclinic or a GP who's a community health partner. It's supposed to be among one of the better sports medicine clinics in Singapore.
If the pain is genuine, better get it checked out soon coz spinal injury in the cervical section can lead to breathing and cardiac issues (my doctor mentioned it can lead to suffocation or deadly heart irregularities in severe cases

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However... if the pain is a figment of your own device, I would just like to point out that today's medical science does have a considerable range of medical scans and tests developed to verify most forms of bone and ligament injuries, so if you're in NS...