Dear Maliha, this could b a reason as your brain keeps functioning & there are flow of thoughts...!

drink one or two glasses of Warm Fresh Milk like 5 minutes before you go to bed,, (Milk has speciality for one to calm down the brain).. this is the reason, grandmothers (u will find normally in remote areas) give milk to children before they are off to sleep.

try & iam sure this will help..!! I was the same & this helped me. :)