Do you nap in daytime or do you sleep till late in morning. If yes then stop it. you need to change your habits. Try to go to bed early. Stop watching tv or mobile phone etc atleast an hour before going to sleep. Drink warm milk
before going to bed. Even if you not able to sleep do not start chatting on what's app or face book etc. Don't sleep till late in morning. Eat healthy well balanced food. Finish your dinner at least 2 hours before bed time. Also dinner should be light
do some kind of exercise daily. Slowly your sleeping timings will change. It will take time. Have patience.
For more details you can consult me.