M Lody E.
First of all remove all distraction or do not hesitate or angry at little noise or any discomfort. It breaks your concentration on your goal. 2nd, thing is that drink water and stay hydrated and try to put a water bottle on your study place so you can drink water when you need. 3rd, try to sit on your study desk as long as you can. But as you began it you might feel some difficulty in sitting for long time. So in the initial days try to sit to study for 1 hr and try increasing it by a little bit every day