Hi Jontar,
Pleased to hear you have got your anxiety symptoms under control now, and that your situation is improving.
One of the most telling things that you mentioned about your neck pain is that it reduces when you sit up straight. The effect of bad posture, but more importantly, lack of movement is key. When sitting poorly, the likelihood is that the structures on the front of your body around the sternum, pectorals etc will get tight. Link this with your previous smoking (and the effect that will have on your diaphragm) and it will lead to a lot of restriction through your rib cage and thoracic spine.
If you cannot move appropriately through these areas, you will begin to overload the structures around it (neck / lower back etc.). The pain that you experience referring over your head / into your eye would link with the referral pattern of Sternocleidomastoid (a muscle commonly associated with poor posture - see attached image).
I suspect that until your mobilise your upper back and correct your posture, this issue will continue to cause some difficulty, regardless of how much treatment your receive to the neck in isolation.
Hope this helps, but please let me know how you get on.
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