Like fellow Huffington Post blogger Yoni Goldstein, I too figured out safe sex without classes. The problem is, not everyone is like us. Even those with the "slightest modicum of common sense" can get tripped up in the complex world of sexual health and sexual relationships. If common sense were all it took to keep one healthy, then I wouldn't see so many sexually transmitted infections and unintended pregnancies walk through my office door. There's a lot of know: pregnancy, periods, erections, contraception, modes of infectious transmission, normal anatomical variations, and the physiology of desire, arousal and orgasm are all complex topics.