Can my backpain be associated with my carseat?

Could be. Yes, I have some patients who are only comfortable in their own car but cannot drive their spouses car due to back pain. There are so many variations in seat design that what is good for one person may not be good for another.
Maybe. Some back pain can be associated with prolonged driving and staying in 1 position for many hours. Also, older vehicles with poor shocks may result in back pain due to increased vibration and forces transmitted to the driver.