Yes, your weight would put you in the 'dangerously underweight' category (if you didn't have a heart attack first), but unless you actually had the psychological symptoms of anorexia you would not be classified (you would, however, be sent directly to a hospital.)
You shouldn't aim for this, anorexia is not a lifestyle, it is not a fashion statement, it is not a 'new fun diet', it is a serious and dangerous psychological disorder that kills (around 20% of anorexics die as a direct result of the disorder).
If you are this underweight, go and sign yourself into the nearest hospital and get help. If you are just another silly teenager wanting to look like a model, don't.
Anorexia ruined my life and will ruin yours too if you let it.