Possible BiPolar? Or passive argessive?

Okay, I don't know how to explain my mood swings in a post but I'll try my hardest.

You see, I'm a dancer and the only time I can control my mood is when I'm dancing. It makes me really happy and I love it.
But, when i'm not the smallest things may irriate me and make me so unbelievably angry I can't explain, or make me really upset. I always used to be extremely optimistic, althought, over the past few weeks (nearly a month) I'm finding it really hard to be optimistic, I get angry at the stupidest things for instance, my sister told me to put all the leeks in one bag and I was fuming!! I sulked all the way home in the car like a little child I wouldn't talk to anybody and bare in mind I'm 16, but then about 15-20 minutes later I got home and I wen up stairs with my sister to watch a film and I was on top of the world... I dunno whether that's just normal teenage mood swings?

Also, the other morning (this has happened a few times recenty) I woke up in the most awful impatient agressive mood, my mum tried to cheer me up and I just got angrier at her. My brain was doing flips I ccouldnt control how annoyed at her I was. And that lasted all morning but then when it was the afternoon I was absolutely fine, I was so happy.

I used to say lifes goes on, that used to be my moto but now it's more like why bother? I can explain it, if I can't do something well I'll purposely not do it right after I've done it wrong the first time but I don't mean to... If you get what I mean? I don't think it's bipolar, but I realy don't think it's normal teenage mood swings...

Help please...? Really frustrating me because I can't explain this to other people they just think I'm a moody cow.