If you bring home herpes, gonorrhea, chlamydia, or something worse, there is no way to get out from under that with your girl. She will resent you forever and even if she doesn’t break up with you, your relationship will never be the same and she will never ever trust you again.
So just wrap up your junk. I know it sucks and doesn’t feel as good but neither does a burning pain when you have to pee. Think about it.