Yes, I've taken it twice, both for condom breakages when I wasn't on the pill years and years ago. It made me horribly ill. It's like taking a really high dose of birth control pills all at once, so can cause nausea and headaches. I felt pretty rough for a couple days. But then was fine. It didn't affect my cycles and I didn't get pregnant. I know the first time it would have been right around ovulation, which is why I freaked out and took it. I can't remember the second time, but I was living overseas in a developing country working with my now-husband at the time, so definitely did not want to take any chances getting pregnant there. Obviously worked both times. I took it probably 24 hours after and I don't think I've been under 175 lbs since high school. It's actually not that it doesn't work if you are, but like most medicines, the dosage is calibrated to the average weight person, which I guess for women is under 175, birth control is the same, so are lots of medicines, and they generally all work perfectly well. They just have to say that to cover their butts. It works by preventing ovulating and making implantation difficult, so even if ovulation already occurred, it can still work. And of course, even if you did ovulate and it was all perfectly timed, it doesn't mean you'll get pregnant. There are loads of factors that can affect the chances of a pregnancy occurring, which is why it takes many ladies at least a couple months of trying. So I'd try to stay pretty optimistic if you still feel like you aren't ready now.