So, do you have other symptoms of ADHD? If it's a big enough problem for you, it might be worth seeing a doctor about to see if you might have it.
And other than that...you say that sometimes hours pass and you've only gotten through 1 chapter? Okay, are hours passing because you ended up doing other things (reddit/tv) or you staring at your book and just barely retaining anything? If you're doing other things you need to remove all of those distractions or go to a public place like a library to study for a set amount of time.
If you are just not retaining information and having trouble "getting through it," you can not spend hours in a row studying. It's really ineffective and affects concentration and memory. You shouldn't study for more than 45 minutes to an hour at a time without a 5-10 minute break. Which should be spent doing something like taking a short walk or eating a healthy snack. When you feel your concentration getting away from you, you either need to refocus your attention, just get centered again and try again. If you can't, you need to take a couple minutes break before trying again. Doing something sensory like drinking a big glass of ice water really helps me.
If studying in silence isn't working for you, try some low volume non-lyrical background music. Are you getting enough sleep and eating a healthy diet?
Are you overwhelmed? You need to get a journal or whatever and specifically break down chunks of your time. Set a 10 minute chunk of time where you will read the first 7 pages of your book. Then take a 2 minute break if you need it. The next chunk of 10 minutes, answer 3 homework problems. Just break it into really small, manageable pieces. I really think you're trying to spend too much time all at once on your work and it's stressing you out/leading to distraction.
Also, how do you study? Maybe it's wrong for your learning type? Some people do well with reading, some need to hear the words (read aloud or listen to recorded lectures again), some need to write it (re-copy notes or write flashcards) some need to make up/look up/draw pictures or symbols that will help them remember. Some people do all of these things. Maybe you haven't found the right method yet.