hi yongleng, welcome to HYDROtribe.
To gain weight, I will presume you are talking about functional mass, ie muscle mass, instead of fats?
You are the typical ectomorph genetically, or what we normally call, hard-gainer. Can I know your age and height?
Sleeping and eating alot are only part of the equation. Physical training is the other. Are you a paddler? It could be your eating pattern as well, ie. what you eat instead of just eating alot of anything that comes your way.