Hmmm. Can you reward yourself for staying on task? And break up the assignments/study time into smaller chunks? Then reward yourself when you get the smaller part done. You might be feeling overwhelmed by the sheer amount of material or assignments.

What rewards might work for you? A small piece of candy? A few minutes break? (You'll need a break now and then!)

Try to interact with textbooks by asking questions as you skim the information, and then go back to see what the answers are. Relate the information to real life or to something significant to you. For example, if you have a list of things that needs to be learned in order, then take the first letter of each word and memorize it and go down the line. You'll end up with something such as "PRMDX." The first letter can cue your memory.

I hope these suggestions will at least be a start. Getting good grades will also be a great reward.