I have realized that all of my symptoms as of now are linked to a neck problem instead of a concussion which I previously thought.

I came to this realization three months ago, at which point I had basically been resting in bed for 6 months, doing next to nothing. This only made things worse (except for in the very beginning). At one point I had extremely bad range of motion (ROM) where I literally couldn't move my head at all, in addition to barely managing to open my jaw.

Some time later I went to a chiropractor who, last minute before I left, suggested I could try to massaging my jaw muscle. I was skeptical at first, but I eventually tried it, and was amazed that it actually made me feel better. At first I couldn't pinpoint what was better. However after a lot of testing, I figured that it actually helped with all of my symptoms. Everything from feeling foggy to vision problems.

Appearantly I have several trigger points (TrP) in my jaw muscle. These TrPs were appearantly making my upper neck tight. I can feel my upper neck relax after pressing on them for even just a couple of seconds. I've figured out I also have some TrPs in the shoulder area and in the upper back. And even pressing on some of these help a bit on the neck. Some of the trigger points might be a result of all the inactivity, in addition to having a tense body because of anxiety.

The TrPs in the jaw also makes the primary jaw muscle tight so that I can't fully open my mouth. How far I can open the jaw varies from time to time, depending how bad the TrPs are. And this is what lead me to the conclusion that all of my current symptoms is because of a neck problem. I started measuring with my fingers how far I could open my mouth; when I could open my mouth far (about two and a half fingers) I felt pretty good, and when I couldn't open very far (one finger with little extra room) I felt worse. I know this sounds pretty weird.

When I came to the realization that the neck was the primary issue, my life made a 180. I started doing things that I only dreamt of just a week before. And three months later, I'm now doing much better (relatively).

However there is one problem I've been having that has held back my neck recovery. And it is really freaking me out...

Whenever I yawn, it really strains my neck, making me feel way way worse. I feel foggy, dizzy, my vision problems gets worse, more noise sensitivity, less ROM, and more lack of sensation in my body. This is incredibly frustrating, because I yawn at least once a day. Over time after the yawn, I feel better and better.. until I yawn again and I'm back to square one.

What should I do when I sense a yawn coming?
Or how could I stop my need for yawning?
Or how could I make the yawn make less strain on the neck?

Any advice would be highly appreciated!

Among other things, I have tried redirecting my attention to another part of the body, for example by pinching myself very hard, but to limited success.

I should mention that I had a sleep study done and got informed I have a moderate degree of sleep apnea, so that could have contributed to the need for yawning. But now, even though I use a CPAP for the apnea I still feel the need to yawn every day. I am probably a bit tired, but being tired isn't that easy telling apart from the foggy feeling I get from the neck after yawning. One thing I know I can do though, is having a more strict sleep schedule.

I had similar issue with yawning, I couldnt yawn for about a week right after my whiplash.

My advice - stop trying to control everything, just let it go.
You need to teach your mind to ignore false alerts, and recalibrate your senses, ignore the pain and accept it,
learn to live with it and it will eventually go away

Anxiety and stress wont let you heal because they will over excite your neurons and wont let your sensitization heal.
Chronic pain and concussion/whiplash can make you develop sensitization,
simply ask yourself had the symptoms changed during the time since the injury?

Central sensitization as a component of post-deployment syndrome

Sounds like the problem is still in the neck. We've had luck with chiropractic that does a gentle/safe neck adjustment called Atlas Orthogonal. The Atlas is the vertebrae your head sits on and is very often twisted after a concussion and\or whiplash. This also causes a restriction in fluids getting to your brain properly. Sounds like when you yawn you maybe restricted those fluids even more causing your symptoms?

When you feel a yawn coming on look down, it keeps your jaw from opening too far. I have TMJ also and that was one of the tricks they told me to use. Hope it helps!