英语里,什么时候用need to,want to ,like to

三个不同程度的需要.简单地举例如下：
1,I need to see a doctor,coz I have very bad headache.迫切需要的,一般是马上会采取行动.
2,I want to learn Chinese,coz I am going to China the end of this year.需要的,不一定立刻采取行动
3,I would like to travel around the world when I finish my school.希望的,但行动可能性占得比列没有以上两个大.