Sorry I missed the word "ended". Your period should start 28 days after the first day of your last period if you have a normal cycle. If you have an irregular cycle it could be earlier or later than that. There is no way to tell. If however you are worried about pregnancy than take a test. If its negative and you still don't get your period in a week detest or contact your doctor for a blood test.
If you have normal 28 days cycles than the 18th of March. If you have irregular cycles there is no way to tell.