Hi,
Welcome to the ehealthforum and I am really glad to help you out. What you are having is anorexia nervosa and in this people may have an intense fear of weight gain, even when they are underweight. For this they may diet or exercise too much, or use other methods to lose weight.
Individual cognitive behavioral therapy, group therapy, and family therapy have all been successful. Talk to your family and friends openly about any fears or apprehensions, eat nutritious healthy food, exercise regularly and join some hobby classes. You may be still in the beginning of anorexia nervosa.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care.