I am not in the medical field and of course no one can provide medical advice but your doctor.
In my personal experience, I had whiplash after a car accident, and then my headaches went from episodic to daily chronic migraine. No doctor was interested in discussing the accident because I didn't technically hit my head on anything. They got progressively worse for years and no one could figure out why until three years later, when I asked for a lumbar puncture, and it was discovered I had a CSF leak. Whiplash can cause a CSF leak, so if you've had everything else checked out, and nothing else is turning up, a lumbar puncture might be a test you could discuss with your doctor to determine if your CSF pressure is normal or too low.