XiaoWei,
since you're a happy student,you hadn't to be depressed by your weight,you'd better to know that your happiness don't rely on your weight,right?So,cheer up.
As you say,you don't like to be fat,but what you have done is on the contrary of your will.A lot of junk food and no exercise at all will certainly make you fail to lose weight,which exactly should be your target right now.
I see people do things,leading to the result of which they dislike a lot,and I am curious about their purpose and their both attention and caution to such effects of what thay are doing.I mean,shoulen't we people be clearly realize what our doings may come?why don't we just to forecast and therefore avoid being silly?that's questions for me,also for you,you may ask yourself what do you want after all.To get clearly aware of your target,then the other things are simple.
you have the words.
Yours
Mr/Miss