it's common - take a break.... drink a glass of water... then go for run... then come back and study
prepare a schedule and stick to it.. Take 10 min breaks every 2 hours and refresh yourself. At the end of the day, you can use your phone, but until then, switch it off or keep it away. Ask your family members also to not disturb you. Close the door, keep a bottle of water, and focus with a calm mind. Follow a schedule and you'll get used to it.