Your way of weight loss is called Crush Dieting, which knocked out your reproductive system, and to a great degree your whole metabolism. Your brain got the wrong 'message' that you are starved and the emergency response is to shut down all non-essential body functions, starting with your ovaries. Levels of your female hormones go down to a low in childhood, menstruations may be missing for months, and your bones will suffer the most and you may end up in osteoporosis (old age problem).
Knowing your body weight and height (before and after your diet) will enable us to calculate your ideal weight for your height and the best type of treatment to help you. A few months of hormone replacement treatment may be needed while you stabilise your weight. There is nothing wrong is losing weight but it must be gradual and in the range that will allow your body's optimal functioning.
The best advice is to see a gynaecologist, in particular specialising in reproductive endocrinology, for advice and treatment if needed.