I don't want to doubt your doctor's opinion when I have never met you, as I am not a professional — just someone who suffers from the same disorder.
I wasn't surprised by my diagnosis at all, as I hear voices and self diagnosed myself as bipolar before I even visited a doctor. This was all when I was 14. Everything will turn out okay if you continue to seek help. If you're seeking help at all, that's a wonderful sign and says a lot about the severity and possible prognosis of your illness.
I wish you the best!