Ct scan ok. what would cause stab/shooting pain in back of one side of head? especially when bending over but doesn't happen every time. andoccasional

Positional head pain: The causes of headaches are enormous in number. Positional changes that provoke headache help differentiate but without a thorough neuro exam are difficult to diagnose. Consider cervical spine disorder, peripheral cranial nerve / occipital nerve cause, or more seriously a spinal fluid pressure cause. I would recommend a neurological exam and an MRI if exam is in-determinant.