I am not sure if I should be worried or not. I had my last period on January 23, and then on Feb 7 flew to Japan from the US. I have been here three weeks and my period is now a week late. I looked online and it said stress, change in diet, and increase in exercise can cause your period to late. I've definitely been stressed the past few weeks, I have changed my diet dramatically (all they eat is fish and rice here, and I've lost at least 5 pounds) and I've been exercising way more (I have to ride my bike or walk everywhere because i have no car!). Anyways, my questions is when should I expect my period to come? At what point should i get worried?

ps i can't be pregnant, im a virgin, so that's ruled out