Honestly, this can just happen. There doesn't have to be a specific reason. If you didn't have protected sex or you did and took a test which is negative, then I would not worry. If the pattern continues with long cycles for about 3 months to 6 months, see your doctor to determine what the cause is (thyroid issues, etc.) but a random late period is not unusual. Try not to worry-- your period should show up. I'd only take pregnancy tests at one week intervals, meaning wait a week before trying again in case it is too early. But in my opinion, simply being 2 weeks late is not unusual. good luck