You probably aren't bipolar. I'm 19 and have a formal diagnosis, but often think I just went through a really 'rough patch'. Having said that, I do still take meds, mainly as a long term preventative measure.
Trust me, you'll know if you're having proper manic episodes because they'll go on for weeks and you'll start thinking you're Jesus and crap. Plus, no one really wants to get landed with a label (I appreciate the irony of saying this on a personality typing forum ).