I think the advice you've got here to try to slow down and give yourself a bit of time to recover is good. It feels at 17 like you have to charge into the future and not wait a second or opportunities will disappear, but it's not really like that at all. Independent adult life is so impossibly big that you can't hope to experience even a tiny fraction of it; what you miss out on will be replaced by things even better.
If you're in a position to hold off a year at school - delay your A levels medically - that might be good. You can keep up with some of the math and programming you enjoy, but don't make it a struggle. In the best case, neuroplasticity will come to the rescue and you'll find you're able to function at something close to your prior level. And if not, some time spent to grieve for the You that had Oxbridge and GCHQ dreams will be immensely worthwhile. You will find that your brain will either adapt and recover, or adapt and make you feel okay about who you are now - today you're fighting against that, and something will break.
The other thought I had is, is there anything that you feel now comes easily to you? Programming no, you mention your poor working memory. But are there other pursuits which feel less like you're pushing up hill? If you do take some time off you may want to start investigating other possible futures for you - things that don't rely on working memory or deep abstract thought.
If you're in a position to hold off a year at school - delay your A levels medically - that might be good. You can keep up with some of the math and programming you enjoy, but don't make it a struggle. In the best case, neuroplasticity will come to the rescue and you'll find you're able to function at something close to your prior level. And if not, some time spent to grieve for the You that had Oxbridge and GCHQ dreams will be immensely worthwhile. You will find that your brain will either adapt and recover, or adapt and make you feel okay about who you are now - today you're fighting against that, and something will break.
The other thought I had is, is there anything that you feel now comes easily to you? Programming no, you mention your poor working memory. But are there other pursuits which feel less like you're pushing up hill? If you do take some time off you may want to start investigating other possible futures for you - things that don't rely on working memory or deep abstract thought.