What causes ur spine to go straight up and down, with no known injuries?nd can this cause neck, back&shoulder pain including headaches?

The spine is straigh: The spine is straight up and down no.

Weakness: Straightening is usually seen due to muscle tightening. It can be due to muscle guarding after an acute sprain such as whiplash or as a result of weakness. Weakness will result in the muscles tightening in an uncomfortable attempt to maintain posture.

Not always one thing: The spine's curves absorb shock when you walk, run, etc. Straightening reduces the spine's shock-absorbing ability and can lead to headaches, back & shoulder pain. Causes for straightening can be arthritis, abnormal vertebral shapes/compression; nerve dysfunction, bone, ligament, or muscle injuries, muscle strength imbalances, etc. A good do might find the source of the problem and correct it.