I missed my period by a week, can I be pregnant ? My period was last on March 14,2012

If you have been having sex, then yes, it is possible. Are your periods normally quite regular? Since it has already been a week, try a pregnancy test. Be sure to follow the directions carefully. If negative, wait another week and see if your period just shows up late. You might even skip a month. Try another test at that time if necessary. If still negative, wait and see what happens when you would expect your period the next month.