Yes, all the above things can affect our cycle and when we have our period. Most women are irregular from time to time. I was last month myself I believe do to losing some weight. Stress, changes in diet, weight gain or loss, changes in routine, illness all can affect when our period happens. So, if you aren't sexually active, then you are fine and just wait for it to happen. It will and unless it goes for three or more months, it is not a cause for concern. good luck hon
Literally the same thing's happening to me. Have you experienced change in diet, extra stress, birth control?(I know you said you haven't been having sex)