Could scoliosis cause mild to severe back pain and severe tension headaches?

Yes. It can, if coupled with c-spine or thoracic abnormalities, contribute to uncontrollable repetitive movements. You need to be seen by a good Neurosurgeon who can evaluate your cervical thoracic and lumbar spine. I suspect there will be other findings beyond the scoliosis. Good information is available at http://www.srs.org/patient_and_family/scoliosis/early_onset_scoliosis/tis/index.htm.
Sometimes. Patients with moderate to severe scoliosis may develop pain as they age. Depending on the location of the scoliosis and the physical fitness of a person this pain could be mild to severe or contribute to headaches.