Oh, nuts, your post came up on the questions list as being in the "Trying to Conceive" community but after I answered, I see it has been put in the Fertility community. So never mind my first question.
Anyway, periods can be a bit irregular for a while when you are within a year or two of having them start up. Don't' worry.
Hi, although you have posted this in "trying to conceive," I assume you are not trying to conceive? It's pretty normal for a period to be a bit irregular when you haven't been having periods very long in your life. I would not worry, unless, of course, you have been having sex.