STD/STI

Okay, so I just recently heard a rumor from a couple different people, that a woman that my ex had sex with, carried some form of STD/STI. I've been panicking ever since, because we have obviously been sexually active since their relationship. I'm getting checked eventually, but I've shown no symptoms that I was curious about. I had a bump on my labia majora, and I squeezed it and a white substance came out from it, like a pimple. What is that? Any tips? I'm a little spooked about the whole entire subject.