Young people your age tends to think you're misunderstood and neglected, or incompetent and inadequate, and many more. That's why you try and hurt yourself or do things that can get the attention of others because you want to prove that you matter. I'm not saying that what's happening to you is done by you on purpose, it's just a possibility and maybe you just don't realize it yet.
Let me give yu some advice. Wise up and start thinking. If you are in control of this behavior then stop it immediately and if it seems to you that you are suffering from some sort of mental health issue then immediately consult a doctor. This are the responsible things that you can do.
Instead of worrying about your looks, you should be thinking about your studies. Unless of course you have a high degree of narcissism in which you should really consult a psychologist. You're young so early diagnosis and treatment is vital do that you can overcome this problems now and have a better future.