Yes, it is normal to miss your period; however that does not mean there is no cause for worry. Menses is controlled by hormones that keep the body balanced. Missed periods may mean a disruption of that balance. Medically, the absence of a period can be placed in two categories, amenorrhea or oligomenorrhea.
Amenorrhea is the absence of one or more periods. Amenorrhea is diagnosed when a female has started her regular periods, but missed three periods in a row or when a female has not had a period by age 16. Oligomenorrhea is diagnosed when someone has started their regular periods, but the periods then become infrequent or the flow significantly decreases. Oligomenorrhea may be the symptom of a bigger underlying cause such as mumps, thyroid problems, or anorexia. Other less severe causes of missed periods include stopping birth control like Depo Provera, obesity, stress, or strenuous exercise.
You should see a healthcare provider for any missed periods to assess all possible reasons for your missed periods. I know you said you weren’t sexually active or on any birth control at this time, but have you ever? It only takes one time to become pregnant. Pregnancy is the most common reason for amenorrhea. You really should visit your health care provider to discuss this matter because pregnancy is not the only consequence of sex, you can also get a sexually transmitted disease. If you are not sexually active, I applaud you and strongly encourage you to remain so. Abstinence is the best option to ensure continued sexual health.
Hope this helps!