What Causes Forgetfulness?

Hi, my name is Angela, female, 25 years old. I´m from Uruguay in South America.
Since I was a little girl I forget everything! When people talks to me, or when I´m reading I have to ask again, because my mind fades away. (sorry for my bad english)
I feel tired every day, I have to work hard to do anything.
My neurologist told me that try to do activities that makes my mind work. I also tried with mathematical exercises but doesn´t work. She studied my head but coldn´t find anything wrong.
Till I had 6 years old I had anemia, very hard one.