Is this normal? Help please? Girls only.?

Okay. This is about my period. My period has been regular, I first started February 9, 2011. (This year.). It was regular in March, April, but in May it started 1 day late. But that's okay. I had just started, so I wasn't expecting my cycle to be completely regulated yet. So in June, (this month) I started 2 weeks early. My family and I were in the process of moving, so my nana said it started so early because I was under a lot of stress. But now, June 30th, my period had started again. And I already had my period this month. June 2nd to the 12th or the 13th. But now we're on the 30th, and it started again. Why is my period coming in early and more than once in one month? Could this be a bad thing? I'm not sexually active and I'm only 13. Please help me. Thank you.