Thanks for your question. Taking one birth control pill after sex will not prevent a pregnancy because it is not the right dose of medication. In this situation, I would advise taking Plan B to prevent pregnancy within 5 days of the sex (Plan B is more effective the sooner you take it after sex). You can get it over the counter at the pharmacy, or many youth clinics or STI clinics give out Plan B for a reduced price (or free). You can use our clinic finder to find the nearest clinic to get Plan B – search using your location and select “emergency contraception” under “offering this service”.
Let us know if this helps or if you need more information,