Don't freak out!
Periods are not only bad because of PMS, cramps, etc but because they love to mess with us. It's really not unusual for them to a day early to a couple days late. There are so many factors that cause all that. Stress, diet, exercise, lack of sleep, too much sleep, if you've been sick, or just because your period was lazy haha.
I would just chill out. If you don't get it in the next two days, I would just buy a home pregnancy test.
Best wishes!
Megan