Hi,
Welcome to ehealthforum.
All family planning methods are associated with some amount of failure rates specific to each type. It depends on which one you are following to guide you on your chances of pregnancy while being on it. If you are following it is correct method and have not defaulted in between, then chances of pregnancy are less.
Wait for your periods to start, they can be upto 10 days late in few instances. If they do not start even after 10 days (since your due date for periods), then go ahead with an examination by your gynecologist along with a blood HCG level test to confirm/rule out pregnancy.
Take care.