School needs to be told if you're still unwell and the stress and strain is making you feel worse.

These accommodations I was talking about would only be temporary until you're able to concentrate better and need less rest. Your parents would organize all that with the school. You'd need a doctor's letter outlining the situation. Schools/teachers would be or should be aware of the limitations of a recent concussion. The fact that you're having problems with it doesn't mean it'll last forever, it just means that you have a teenage brain and that you haven't fully recovered, yet you're wanting to keep up in school.

Schools/teachers would know the drill for students in this situation.

Part of the way you're feeling again now may be because you've gone back to school and the stimuli of busy classrooms and hallways can be very overwhelming let alone having to keep up with work and homework etc..

You're still very anxious by the sound of it. I know it is frustrating for you, but you'll get better.