[Always *]

Well, as you said yourself, literally anything can throw off your period, and it could be something as completely random as you're diet or exercise patterns changing to something more serious, which could also be a ridiculously long list of things, including something seemingly unrelated such as if you recently had the flue. Your body could have suddenly decided it wants a different cycle too and that could easily come with new symptoms. Generally, if you're not experiencing excessive pain or very heavy bleeding, I wouldn't worry too much. If it happens again, you could always follow up with your doctor.

Birth control is a super great way to regulate your periods, fyi, great thing birth control lol