Condoms suck, but be a hypochondrial Edited. Profanity and masked profanity are against forum rules and may result in discipline. and watch the movie "Kids".
The girl might be going through some mental stress that's throwing her body out of whack. I remember in high school I knew this chick going through a similar situation. Anyway, after her negative pregnancy test result, she got her period. Conclusion: it was the stress that was throwing her off.
Then again I knew like 700 other chicks in this situation that had kids 9 months later.