Just a few quick points.

I find it strange that your GP stated you couldn't do any more damage. Of course you can, dont be alarmed, this is just the natural degeneration of the spine u will be more susceptible to with your injured neck. This is also the reason your neck has been getting worse. The straightening of your neck is also a natural process. However i more commonly see a more curved or forward head posture in my practice.

My advice to you would be dont stress, as for starters this can make your chronic pain worse. Ask around for a decent physiotherapist in your area and get them to give you a decent assessment. There are many ways you can manage your pain and symptoms. The easiest being heat packs, something you can do at home without a physio.

Keep us posted