Hey I can completely understand why you are so devastated over your hair loss, especially at the age of 15. You have done the right thing by making a doctors appointment, because to be blantantly honest, he/she is the only person who is going to be able to fix this problem for you. There are multitudes of conditions and disorders that could be causing your hair loss, and without doing the tests and investigations, it would be near on impossible to diagnose. Once your doctor has done all the tests, he/she will treat you accordingly, and i'm sure your hair will be growing as strong as ever. It is obviously some kind of disorder or condition causing it, as you are far too young to be losing hair naturally. Good luck with your appointment, and I hope they find the cause very soon.