I can't sleep more than 2-3hours. i get awake then unable to re'sleep. why is that so ?

Common: This is a common situation. Approached systematically it might be resolved. Avoid caffeine (coffee, tea), tobacco and alcohol if you use any of these. Go to sleep at the same time nightly. When you awake get out of bed and read something spiritual for 10 minutes, then back to bed. Avoid sleep medicines if possible. They usually stop working. If necessary see doc for thyroid check, etc.