My advice would be to stop trying really really hard. If trying to read a book does your head in then don't do it - you can't really achieve anything much when you're in that state. You need to bore yourself back to health, then you can learn all the history and maths you like.

Try and do simple, easy, peaceful things that you find pleasurable - don't go for walks, get a friend to drive you somewhere and just sit there, birdwatching or something. Enjoy nature in a way that doesn't exert your brain or body, and don't try to learn anything.

Yes it's depressing and boring and it feels like your life is indefinitely on hold, but when your brain is telling you it's overstimulated, you need to listen to it. It sounds to me as though these challenges you are setting yourself are indeed doing more harm than good.

Hope that doesn't sound too patronising, it's not meant to be cos believe me I did all the same stuff - though by nine months the PCS had truly beaten me into submission and I would no way fight against it anymore. Maybe you just have more willpower than me! But really the symptoms are your friend - they're your brain's way of trying to make you give it the rest it needs to heal