Misdiagnosis led to decades of unnecessary suffering. Do I have a medical malpractice case, or personal injury case?

You did not state the date or dates of the alleged negligence nor the actions of the doctor that are in question.  However there are time limits for filing a lawsuit that you should know to determine if you still have time to file a lawsuit.  Below is the relevant wording of California Code of Civil Procedure Section 340.5 that governs the lawsuit filing time limits. In an action for injury or death against a health care provider based upon such person’s alleged professional negligence, the time for the commencement of action shall be three years after the date of injury or one year after the plaintiff discovers, or through the use of reasonable diligence should have discovered, the injury, whichever occurs first. In no event shall the time for commencement of legal action exceed three years unless tolled for any of the following: (1) upon proof of fraud, (2) intentional concealment, or (3) the presence of a foreign body, which has no therapeutic or diagnostic purpose or effect, in the person of the injured person. Actions by a minor shall be commenced within three years from the date of the alleged wrongful act except that actions by a minor under the full age of six years shall be commenced within three years or prior to his eighth birthday whichever provides a longer period. Such time limitation shall be tolled for minors for any period during which parent or guardian and defendant’s insurer or health care provider have committed fraud or collusion in the failure to bring an action on behalf of the injured minor for professional negligence.