I can't sleep regulary and I don't know why!

There could be a lot of reasons for this. Best advice is to go talk to your doctor so that you can get this under control. It may be something as simple as diet/stress,... and it could be something more serious. Best wishes.

Lets start with with broad questions. How is your diet? Do you drink a lot of caffiene, take drugs, smoke? Do you have feelings of anxiety, are you afraid, are you worried? Does something from your past haunt you?

If you can answer yes to any of the above, can you pinpoint some things that your thinking?

What is your sleeping arrangement like? Are you alone, do you have a room to yourself? Is the tv or music on? Are you too hot or cold?

For me, sleep has not often been a problem. But when it is, getting the room as dark and as quiet as possible is a good start. Then I do my best to think happy thoughts. Finally, and most importantly, I close my eyes and kep them closed. Eventually I fall asleep.

If it is more serious and you can't help yourself out, you will want to seek professional help. I don't agree with drugs like Ambien unless absolutely necessary, but maybe a pshychiatrist or even some hypnosis.

Losing sleep isn't healthy for many reasons, too many to name. I used to work overnight/graveyard shift and after I quit it was a tough readjustment. I started exercising at night to make myself tired and I would take my dog for walks, stuff like that. Sometimes I would lay in bed, listening to the radio. There are also things like meditation, praying, breathing techniques and things like yoga to relax your body to get your mind off of whatever bothers you at night. I picture you thinking a lot. Do you worry a lot about others? Do you worry a lot about yourself? Things like this are usually related to stress and you can talk to your doctor about what he thinks, too. That's what I ultimately benefited from the most was talking to my doctor. But there's a difference if you can't sleep because you don't feel mentally ready to fall asleep or if it was because of a job/commitment or something like that.

Wow. I would go talk to your Doctor and see if he can give you something or see what the problem is. I hate not getting enough sleep.

Don't drink tea or coffee or chocolate after 6 oclock pm, have some yogurt at nights. yogurt help falling sleep. When you go to bed, read books until your eyes are tired then close your eyes, take 3 to 5 deep breaths and then imagine a white surface and stare at it until you fall sleep. Or count the imaginary sheep :p Oh, And don't think of nything like school, work, problems and stuff from an hour before you go to sleep. some people who suffer from insomnia are cured when they are taught not to think about anything before going to bed. Meditating before going to bed could also help.
GOOD LUCK