Because you had unprotected sex ALL an egg needs is 1 sperm - in one ejaculate there are 1 million sperm, in 1 drop there are 10,000 and in precum there can be upto a thousand sperm - depending! You can't see sperm so you can't control if you have any on your penis or not! ANYTIME you have unprotected sex you are playing Russian Roulette and it is just a matter of time for you to become pregnant! ALWAYS protect yourself! Also a baby could be the least of your worries! As genital herpes is a HUGE problem right now, and if the present stats continue 1/2 the population of the USA WILL have genital herpes in 10 years!!!!!!! There is no cure for Herpes!! So hopefully she isn't pregnant, time will tell, and think more about your health and hers from now on OK?