Much more information is needed in order to answer this question.
Previous menstrual period? Did it come at the right time and was it normal? Do you have regular periods?
Sexually active?
Have you performed a home pregnancy test?
Using birth control, and if so, what type?
Is the right sided pain still present?
Has this happened before?
What is your weight and any large weight changes? Are you under a lot of stress?
Ever had issues with your thyroid gland or family history of thyroid problems?

Ray A. Wertheim