Hi, theguyonline, welcome to PsychCentral.

I don't have ADD or ADHD but a lot of your story sounded like mine. Sounds like you're not as interested in your studies as you are in being online and messing around.

To read your textbook, I'd do it a little at a time. Not make yourself site down and "read" like you've probably been trying to do but instead, explore what you have to read, find interesting (to you) parts of it to read, etc. Read first sentences of paragraphs only, maybe, for a bit or first and last sentences unless you find paragraphs that seem more interesting and have something you want to know.

Make up a game with your reading; translate it into your native language?

I scored in the 99 percentile on a nationwide maths test but was only getting a B-/C+ in that maths class. Einstein flunked maths.

What course is your reading in?