Questions about injury

I suffered a concussion last year, which the hospital report concluded as a moderate to severe concussion. Even tho it has been about a year I still suffer from different symptoms, what appears to be called post concussion syndrome.

Would this type of injury be considered a tbi?

Why are my symptoms delayed?
When I get headaches, pressure in head, pressure in neck, brain fog, inability to concentrate, fatigue is not right away. If I push myself doing something physically, or expose myself to too much sunlight. It takes a while or a few minutes for my symptoms to show up. Why is that?

And when they do, I slowly start getting worse. So its hard to tell at first and I have to be careful because when that happens, I cant think straight so I dont crash physically and mentally for the rest of the day.