Its called Insomnia, and I also suffer from it. I can be awake for 40+ hours and only sleep for 4-8 hours and feel completely awake. Even though my body is tired my brain is not, and I just can't fall alseep by forcing myself to (laying in a pitch black room of pure silence)
If old enough, drink some alcohol or get some sleeping medication. Even a couple benadryl might help, but don't do both!
Just don't overdo it or you will become dependant upon it, which you do not want because then natural sleep becomes near to impossible. Only do it in severe cases of Insomniac nights
Some people just cannot fall asleep as easily as others, if you want a more natural solution I reccomend sleep therapy music with earbuds in: ya know, peaceful waves at the beach, a rainforest, etc. Anything that might help you just relax and have good dreams :)
