I'm addicted to sleeping. whenever i sleep less than 6h (ex. 5h), it makes me feel not good. is it a disease and any preventions for this case?

No disease.: Everybody needs sleep -- usually 6-8 hours a day. Surprizingly, some people need 8-10 hours of sleep to feel rejuvinated! in your case, you should sleep for 6-7 hours so that you can be well rested each day. Most people's bodies are not designed to be adequately "recharged" after only 5 hours of sleep.

Everyone's different: Some people get along fine on 5 hours of sleep while others need 8 or 9 hours a night to feel rested. I would guess that most people don't feel we'll with less than 6 hours of sleep. I think that is completely normal and i wouldn't worry about that.