You COULD be. I assume you are sexually active, if you are not then you’re most definitely not.
When was the last time you had sex? Did you use protection? Are you on any kind of birth control?
I recommend you go get an HPT test. If it comes out negative, wait another week, if your period does not arrive take another or go see your doctor to get blood tests.
The best way to tell is through an HPT test or blood tests.
Do NOT stress, it can prolong your periods absence. Try to keep yourself busy with school work, drawing, any hobbies, cleaning, etc.