STI sir, it's an STI. Therefor, 1 or 2 pills and you're good to go. Go to a planned parenthood asap, I don't believe they talk to your parents if your over 16, so you should be good. And only 1 of you needs to go. They automatically prescribe both people the antibiotic.
Sister works at an uber shady PP in San Diego, I know pretty much everything about this stuff. The stories she tells....