Its possible that your MRI is wrong but its also possible that the MRI turned up something minor and the doctors are not telling you about it i suggest you politely request copies of your reports. Also MRIs are not foolproof and they can sometimes fail to pick up relevant problems.
When was your accident after the trauma you have suffered it may take some time for your symptoms to settle down the doctors may actually be right and your symptoms could resolve in time.
there are other conditions such as mechanical dysfunction and abnormal curvature of the spine that can cause pain. Abnormal curvature can be seen on x rays but doctors often downplay there significance.
Yes you are entitled to a second opinion but it could be the same as the first but i would still seek one if i were you.
Good luck nosleep