I had my period twice last month two weeks apart exactly my second period was just as ormal as my first but now into the next month 29 days apart from the last period I have no period? What could this mean?

I had my period twice in one month two weeeks apart exactly the second period was just as normal as the first but now the next month 29 days from my last period I haven't yet received my period for this month should I be worried?