[Age of Ignorance]

Long story, but I'll try to sum it up as much as possible. My sister recently announced to the family that she's pregnant. My sister's 16; her boyfriend is 18 and he's a total social degenerate. He lives with his friends in a flat that he can't pay for, he drives his dad's car without a license, he has no job, broke a contract with a professional sports club because he was too busy playing Call of Duty to get off his lazy ass. My sister's having an abortion this thursday.

Ever since she told me, I've been worried about my girlfriend and I's relationship and our sexual tendencies. On average, we have sex 2-3 times per week. She's on the pill, but I'm unsure what it exactly is. For four months, she's skipped her period (as in, took skipped the 7 day withdrawal tablets in her box). So, so far, I've never been able to be certain of whether or not she's pregnant.

The other day, she took a pregnancy test. It was 5 days before her period was supposed to start. It came up negative. I was relieved, but still had that nagging thought that there's a possibility.

I mean, there's always a possibility... but here's a few questions:

How effective is a pregnancy test 5 days before the fourth time someone skips their period?
What're the odds of getting pregnant from the pill combined with pulling out, especially when done "properly"?


Thanks in advance.