Ever since I had a minor head injury two years ago, my brain has had cognitive problems, and I often feel like I have 'brain fog' if I think or concentrate too hard, even for basic things like reading and maths.
Today I went to DD's math's café they have sometimes for the parents to see how the kids are getting on. Helping her do some of the maths problems was ok but I generally feel scared as my brain sometimes feels like it is wading through treacle or mud when I am thinking, and there is something physically 'in' my head stopping my thoughts (if that makes any sense!)
I've told my GP about it and she says everyone gets tired sometimes after doing intensive mental activities, but I'm sure I shouldn't be feeling like this after doing basic maths for Year 2, or reading a magazine article on an unknown topic... 
It's almost like my brain has lowered cognitive reserve and resources, and that there isn't a way of making it go away once it has started. I just have to rest.
I'm petrified this is just the start of the long slow road to dementia or something. I'm only 36 - I have my whole life to live and can't fathom the thought of my mind - which I once considered pretty good and intellectually sound - to decline. It's just so depressing.
If I ever get Alzheimer's, I'll be out of here. It must be so awful. 