Pregnant woman can have a discharge called implantation bleeding. This is when the egg burrows into the lining of the uterus. Not all women see this during pregnancy, so it's not always something to look for when trying to figure out you're pregnant.
I wouldn't listen to other people. Always have yourself protected one way or another. That way, you won't be nervous and freaking out when things like this happen.
Always have a form of birth control around. I'm begging you, don't listen to other people because they sometimes have no idea what they are talking about. As a teacher, I overhear what some students think...and I'm appalled! Keep yourself protected, ok?
Good luck!