Warren gave you good advice. He is wonderful with the excellent advice.
I would say this...either you have had a lot of therapy in your time, or you are more self-aware than most 15 y/os. That this worries you means you are aware of it and you find it uncomfortable. I think this is probably "normal" teen behavior. I have teenagers, I have raised 3 out of being teenagers and these sorts of mood swings are what I have seen in them.
I can say from the perspective of a parent that the time from nearly 15 through age 16-1/2 is HARD. The mood swings one associates with adolescence seem to reach a peak, seem to switch more rapidly. I know I worried that something was seriously wrong with my oldest son when he was that age. One minute was a darling fellow, so considerate and kind and be throwing things the next, then fly into a crying rage at the world. He is as even tempered a man as I have ever known now. My oldest daughter was the same way and now she is very even tempered too.
I am studying counseling psychology and I have taken developmental psychology. According to Erikson, we all go through the 7 major stages of life. For adolescence, roughly age 15 to 19, the struggle to overcome is identity versus diffusion. This, put more simply, is learning about who you are and what makes you tick. It is a time of self-discovery and identity experimentation. That is all well and good, it needs to be done. However, people this age are also trying to grow to their mature height and build. They have serotonin cycling differences and because of school and work and other scheduling demands, they run around overly tired. They tend to eat more meals outside of the home and many eat too much junk food and not enough "grow food" to fuel their growing changing bodies, and their growing changing brains. If you live in the US, this is not an easy place to be 15 because of the mixed messages about sex, about education, about moral values, and these things add to the pain of figuring out who you are and who you want to be. Just how does someone with a less than optimal diet, lack of sleep, and self-confusion cope with it all?
My grandmother used to say: This too, shall pass. Ohhh that used to infuriate me!! What did she know anyway? Turns out, a lot. It may seem patronizing and trite, but this that you are going through is going to pass. I am less concerned about your having bipolar than I am about your skills for taking GOOD care of YOU. THIS is the time to put into place self-nurturing activities. Figure out what legal, safe things help you feel better. Is that a good night's sleep? Is it a bubble bath? Is it cooking for your family? Is it warm tea on a chilly winter night? Find ways to be gentle and good to yourself. You have to live with yourself all the rest of your life. You have only one body, and only one mind, only one psyche. Treat it with kindness and patience. Love yourself as much as you would a best friend, and be as loving and polite to yourself as you would to your best friend.
Most all, and what one lesson I'd love to teach every child and every teen in the world it this: Learn to forgive yourself. Don't endlessly judge the things you do and say. Don't be afraid to say your are sorry to others, but after you do, forgive yourself. When you don't live up to your expectations, forgive yourself. When you get angry and say or do something you wish you hadn't, learn from it, but forgive yourself.
The baggage of life is heavy for everyone. Why add to it with guilt, shame and loathing? BE GOOD TO YOU, because YOU COUNT and you ARE worth every good, positive and wonderful thing that comes your way, today and always.
The Lady Dragonfly
Yes, it was me...I know because I was there when I did it. Lupus sufferer, bipolar II sufferer. Currently on Indocin for chronic pericarditis related to lupus, and cherishing every deep breath without pain. Currently in graduate school for mental health counseling, class of Fall 2007. Vegan and loving it!