Am I bipolar?

My boyfriend has talked to me about my mood swings. At first I thought it was just my period. But they've gotten worse. Sometimes I'll be extremely happy, and nice. And then if he says one thing that isn't a big deal, I get really mad and irritated for a while. And then I go back to being happy later. During these episodes, I say things that are rude, and mean. But I don't mean them. I don't want it to affect our relationship. But it is getting sort of hard to control my anger. Could I be bipolar?