What you are dealing with right now is "change" and the anticipation of what that "change" means too.

Any kind of change can really trigger PTSD symptoms. And with PTSD there is definitely a strong urge to "flight" which means wanting to get away from a current environment or even a job or anything in the "now". This is how the amygdala hyjacks the brain and presents the primitive "fight/flight/freeze" that people who do not experience it first hand fail to understand and present their "just" comments that the person who is struggling tries to do and yet can't seem to do.

The reason why it can be hard to concentrate is because the brain is simply distracted a great deal when PTSD takes place.

I have read that a person can slowly get their brain out of how the amydala has hyjacked the brain, however for that to take place, the proper "help" and support is needed and the person has to work on "learning and doing" and slowly creating a new sense of structure that feels "safe". However, unless that is supported properly by not only professionals but others as well, the person really struggles to regain control and switch out of how their brain is now hyjacked by the amygdala.

In order to achieve that, often a person will need to learn not only about how a trauma has affected them, but often their own developmental challenges that led up to that reaction to a trauma, as well as whatever challenges they had after the trauma too.

There is a lot of study going into trying to understand this very complex challenge too.