If you are below 18 please do not self medicate. You are not even sure about what happened.
It is not safe practice and henceforth please be more careful. I would advise you to refrain from taking a chance and at least use a condom during intercourse.
Not just for pregnancy
but also to protect from transmitted diseases.
For now please see a gynecologist who will keep this confidential and help you take the right medicine.
Please do not self medicate with the emergency contraceptive pill
as it will disturb your hormonal