Ok, just calm down! If your peroids have just started they wont be regular. So they wont every month, it might be more or a bit less. Its perfectly normal!
This month was supposed to be my second period I ever had! And it didn't come! And my first period lasted for 7 days..!
You don't say how long you've been having your periods, so it's hard to answer. Every girls cycle can be different...in the # of days it lasts, how often she has it, etc...but usually 28-36 and once you've been having them for a year or so you'll better know what is "normal" for YOU. You always count the days from the day you begin bleeding, as day#1.