Don't worry, I hope I can help out some how XD when I was young I also had problems kinda like that. For studying I had to find something that would make it fun and interesting so I wouldn't just get bored and give up on studying. And that was music. Believe me, I cannot stand to study otherwise, if I try to do it without it i give up five minutes later. Also, try different methods of studying, not just re-reading books(that takes to long and you just get bored of it and want to end it and you rarely pay any real attention to it) This is what I do and it's supper useful: I take whatever I need to learn and get some index cards and on one side I write a very short question, like what year this x thing happen? and in the back a short answer, or I just write a name of a historical character for example and on a back what he or she did(what ever you need to know
on the first couple of rounds I let myself read the answers, but afterwords I make myself answer them without looking(that make your brain think, so when somebody asks you about it you'll be like "Oh, I remember I got this asked before!") obviously check the answer afterwards
And if you can get somebody to ask them to you later(and out of order) it helps even more! . This method seriously helped me a ton. I also recommend reading something at the same time as you do like a "vocabulary" were you just write all the terms/characters/facts and write what they mean/are, I sometimes do this two times and it also helps.
And the dislexia can also be part of ADD, because similar things happen to me, it's not actually dislexia, it's that you're brain is to distracted XD(in the past paraghraph I have written like 6 words in the wrong letter order XDand if I read things fast I am most likely to read a word or to wrong, since my brain just jumps to the closest word XD this is because I have no patience ) The only cure for fixing the reading problem, is, well, reading XD suggestion: get books about things you like! no boring school books! start with easy, fun books. This helped a lot with me, now I'm a complete bookworm(and this seriously help you're analytic skills, so it helps in for class, two birds with one stoneXD) If you like reading in english I know a bunch of easy books that helped get me started! And you probably can't get your self to do more things you like is because you hang with that overall feeling that you're supposed to be doing somethings else-most likely school related- at least that's what happens to me a lot XD Oh, and one omore thing, start studying at least 3 days in advance XD don't leave it for last minute(lazyness is a by product XD)
All this takes times, but it is possible, you just have to take things little by little. You don't have to do all this things to the point, it's very important that you make it your own
You can try googleling "good ways to study" and I'm sure you'll find a bunch of other methods
I seriously hope you can get better at all these things
JUST DON"T GIVE UP. I've almost failed a bunch of classes before but now I'm on the honor role, so I believe that if you give it time and you really try you can really work things out!