Greetings, Incognition, from your future self!
Well, not really, but I could easily have written your post nearly word for word when I was 6 weeks along. I went through exactly the same issues.
6 weeks is great, but it's still very early in the overall scheme of things. It takes time to undo the damage. I started keeping a pen-and-paper journal early on in sobriety (around 6 weeks, actually), and early on it's full of rantings such as "MY BRAIN DOESN'T WORK RIGHT ANYMORE!!!", as well as cross-outs and re-writes and blank spots where I got stuck for a word. Nowadays it's much cleaner, as well as reflecting a much more serene state of mind.
Even after 4 years, I still have vestiges of cognitive issues. For example, it still takes me a long time to write a post, and typically I have to go back and edit heavily many times before my writing approaches coherency -- thank goodness for the backspace key! -- however, things overall are MUCH better now than they were at 6 weeks sober.
I sympathize with the feelings of frustration and despair and remorse along the lines of "what did I DO to myself?" But really, there's no point in indulging them, and you must try not to. All you can do is continue to do the next right thing (as you have been doing), and try to be patient. Of course, not picking up a drink is the foremost of those things -- if you stay sober, there's at least a chance that things will improve. If you drink again, there's NO chance.
I hope you'll continue to post as you are able, and let us know how you're doing.