Dear Anannya,
first, leukemia at your age is not that uncommon. Secondly, your doctor knows what works there and you really really really should follow his/her advice. With proper treatment, patients with CML live, period. You are more likely to die from an accident than from your disease. I understand that all that is a chock to you, but you will adapt to this new phase of your life, and things will go very well. You will live, but you must start treatment now. The mental part will come in due time, you will be just fine. Keep us posted.
Jerome