With my first baby, I had three false negative tests before I finally got a positive one (8 weeks by then) which they then double checked with a scan to make sure. And yep, there was what looked like a jellybean jumping around in there.
Big fat surprise, he was. I was 21, halfway through university, dirty great drug habit, drinking like a fish... Luckily my body knew i was pregnant before I did, and wouldn't let me drink, smoke or anything else.
The second one I only found out about because my roommate had a scare and wanted me to take the test with her. So there's the two of us, in the restroom at a burger place (opposite the pharmacy, because we needed somewhere with two toilets to take the test at the same time) arguing about whether the line means you are or aren't pregnant. Turns out it was me, not her. Whoops again!
But I got two big strong healthy 10 pound boys, so can't complain at all, really. No, I wasn't planning them at all, wasn't at all ready to be a mom, but it was the best thing that happened.
Everything for a reason, yeah?