Make a schedule and stick to it with rewards if you succeed, I mean, say you study every night for 1 hour, 20 minutes then 10 minute break, etc until you've done 3x 20 minute breaks, if you do that for a week and make some progress, reward yourself.
In terms of curriculum; best to ask a teacher, they will know the best ways to get ahead and possibly have past exam papers for you to do, this will help and they can also Mark what you've done and let you know what to improve on. Additionally there are plenty of places online that have these and other ways of working through.
My advice is have someone motivate you, a friend or teacher or parent etc, someone you don't want to let down, this and the rewards you give yourself I found was the best way to study and build knowledge when I had no motivation.
I know it's vague, but I hope it helps.
Also, keep a study log so you know what you've done and when and if you slack you can make up for it another day.