Unfortunately, the pill isn't 100% safe. I know a handful of people who've gotten pregnant while on it, so that should tell you something.

When you say you're STD free I'm going to assume that you know this for sure because you've either been tested or you were both virgins. Regardless, I think condoms are a necessity until you are married and can be pretty sure there's no STD risk in the future, and if there's an 'accident' then it's okay.

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Live as if you were to die tomorrow. Learn as if you were to live forever. - Mohandas Gandhi