I used to have it bad when I was in school........until I failed the 5th grade. Before that I only made like Ds and Fs because I would daydream so bad that I couldn't learn. I would start taking a test in school, and wouldn't finish it because I would start daydreaming a few questions in and forget I was taking a test. But something happened after I failed. I suddenly stopped daydreaming, I started reading massive amounts of books (I think over 50 that year) and suddenly I was an excellent student. I started making all As and Bs and I would pretty much remember anything that I learned or read.
It's all in ones head, literally. If you want to deal with it, you have to choose to deal with it, no matter how difficult it is or what it takes.
Drugs and alcohol work for me.....
Practice meditation and I recommend that you do some serious research before you take any meds. They have dangerous side effects and can cause great harm.
Are you in therapy and on medication? That's a start.