I am a straight female. I recently slept with a guy a couple times in the past 8 weeks or so, using condoms everytime. We did have oral sex without protection (both ways). He was diagnosed with urethritis at some point during this time. He says I'm the only one he's slept with in the past couple months, and that he tested negative for any STDs. After first developing the symptoms, he took antibiotics and abstained from sex for about a week, but the symptoms returned after sleeping with me again. (He's now being treated again). I also tested negative for chlamydia and gonnorhea, although the doctor told me to take zithromax just in case. Realistically, what are the chances that his urethritis symptoms were caused by the condom or lube we used (liquid silk, which contains parabens). If there was some kind of non-STD bacteria passed orally or with the condom, what could have caused this and how do we prevent it in the future? If there is some kind of STD involved here, what are the chances it passes orally, and in terms of who's going down on who? Even though I am negative for chlamydia and gonnorhea, could there be some other STD I have that is causing him to have these recurring symptoms? In short, I find it hard to believe that his 2 bouts of urethritis have occured while we both are testing negative for STDs, so I wonder whether one of us unknowingly has been exposed to an STD. All the research of done indicates that this is "rare" but I need a little more context, is it rare like it happens one in a million times or one in one hundred?