Gentle neck therapy would be worthwhile. Anxiety can be a big cause of headaches and other symptoms. The meds may help with the anxiety but nothing more. They are not a PCS treatment. I've never heard anybody mention Mertazapine (Remeron) for anti-anxiety/anti-depressant. Don't know what you should expect.

The sense of not feeling right can be a big cause of anxiety. The PCS makes the brain's anxiety system super sensitive.

Try to relax and be patient. Fighting through will slow your recovery.