Hi Nathaly, birth controll pills are very effective and have a very low rate of failure provided you take it regularly and on time. Even if you miss once or twice it is advisable to take extra precautions as then the failure rate of pills increases. Now what you can do is wait for 1 week from stopping the pills and then do a urine preg. test at home. If it is negetive then wait for upto a week for your periods to start if still they don't come then it would be wise to get an abdominal ultrasound
and a urine HCG
levels to be done to rule out any other cause of missed period. Do visit your gynacologist in such an event. Remember pills are effective as long as we take them in prescribed forma. Take care!