emergency contraception
"I've taken this 2-3 times. The first few times mild cramping occurred but nothing major. The most recent occurance resulted in cramps immediately afterwards and bleeding, I mean heavy period type, 5 days after I took it, a mere 2 weeks after I had started my last cycle. The bleeding lasted about 4 days. I thought perhaps it had reset my cycle but nope, got my "normal" period a few days early and it has been the most painful and heaviest I've experienced in some time. 

Obviously Plan B works, although I have no idea whether or not I was even at risk of being pregnant. Just know it will possibly upset your cycle."