Pregnant ??

I don't understand how people can wonder how they get pregnant but have had repeated unprotected sex???? If you don't want a baby use some form of birth control for god's sake. I've seen countless questions where people are like "what do I do???? I've had unprotected sex 6 times and I think I might be pregnant". Like wear protection or go on birth control. Especially if you say you're 14/15.