I, too, was diagnosed with Occipital Neuralgia following my accident. My GP injected Depo-Medrol into my Occipital points and this reduced my headache considerably. This is only a temporary fix, but, since the Occipital Neuralgia was primarily caused by my neck injury, it lasted long enough for the physiotherapy on my neck to do some good. Also, try icing the back of your head and upper neck to see if that helps.

All the best.