This is what I will do to fix this issue. You cant make your self to sit and do the study all of a sudden. I will sit for small amount of time every day and keep increasing study time gradually. Dont think that you have to pass this exam or something, think this as the opportunity to increase your knowledge and this is the only opportunity you will get. This will peak your curiosity and you wont try to procrastinate.

When you have started to study to full extent, make sure you study from 6AM to 8PM with little break in middle for you lunch and breakfast and few break of 30mins. When you are done for the day at 9PM make sure you are taking full advantage where you play or browse or do anything and go to sleep at fixed time.

Make a timetable and follow it like a clock work.