I feel like i strand a muscle from the base of the left side of my head and goes down to my left shoulder. but my left arm feels like it's kinda numb/?

Radiculopathy: This may be a disc or a spur in your spine pressing on a nerve root as it exits the spinal column in the neck. This would explain radiation of symptoms down the arm on the same side. A neurologist or neurosurgeon would be best qualified to evaluate you and appropriate tests will be done in order to make a diagnosis and recommend treatment options.