I spent my 20s having lots of unprotected sex (very stupid, I know). Luckily I always got tested regularly and never had an STD. Now that I’m a bit wiser, I always wear a condom and also ask the girl beforehand if she any STDs (I’m aware it’s just her word). What else can one do to protect himself?

If the girl lies and has herpes, for example, how likely is it the contagion if she doesn’t have any cold sores?