Hi there. So, you say you are not on any birth control. Are you sexually active and having unprotected intercourse then? When was the last time you did that? You normally can get an accurate pregnancy test 2.5 weeks after the last time you had unprotected sex. So, take a test to rule pregnancy out.
But stress and changes in routine are two things on the list that can make a woman irregular and you are going through both of those now. So, that really could be all there is to it.