Welcome to healthcare magic forum,
Chances of preventing the pregnancy
is about 80-90% but it will be confirmed only after ur due dates for ur periods, if ur lucky enough u wont be pregnant.
One good thing is u have learnt ur lesson from the incident, pls dont have unprotected sex till u get married.
If u dont get ur mestrual cycle on date do the urine test for pregnancy to confirm and see ur doctor for further treatment.
Hope I have answered ur question.