STI transmission

With most sexually transmitted infections, it would be highly unlikely for a person to have one who has not had any kind of sexual contact -- with genitals, hands or mouths -- to have one. We call STIs -- sexually transmitted infections -- what we do because that is usually how they are transmitted...

Here are the possibilities, in order of most likely to least: He WAS with someone else over this last year. I know that's certainly the least easy possibility to look at, but if he really tested all clear before the last round of tests within the amount of time you two have been together, and you...