Trouble sleeping at night

For a week, that I can't sleep at night and I think that may be because of drinking coffee but it doesn't. I usually have a cup of coffee in the morning. After I have trouble sleeping problem then I stop to drink coffee but I'm still have the same problem. I talked to my friends about it. They said may cause with many reasons: stress, anxiety, food, and age which is the last one that I don't want think about. I was searching on the internet to find out that the trouble sleeping called Insomnia.There are many reasons for trouble sleeping at night: over eating, anxiety, or age. For myself, I have to do homework and only sit in front of the computer that may be cause of my problem. I think I should exercise more or have other activities during the day time, not only sitting in the room. I will design my plan for do exercise.