Hello and thank you for taking time out to answer all of our questions. I am a healthy female that has been undetectable for 5 years and I am currently engaged to wonderful guy that I've been dating for almost 3 years. We are currently not using protection in the hopes of getting pregnant. My problem is that over the years whenever he gets sick I am so fearful that maybe I infected him. My question is has there ever been a case of an undetectable partner infecting their hiv negative partner?
This is a very important question. In medicine we like to say. "there is no always, and no never". Meaning, uncertainty happens, as do rare cases and exceptions.
We do know that here have been reports of people who purportedly had undetectable viral loads who have infected others sexually but this is really really rare. For one thing, no one knows what the viral load was at the time of the sex in these cases. Plus, there could be are other factors that could have influenced the risk including the type of sex.
If your viral load is consistently undetectable, and you are super adherent to your meds, research shows that the risk to your partner is incredibly low. But, hard to say it is zero. If he (and you) are ok with this tiny risk (in US risk of transmission from a woman to a man is already lower than the other way around), then you can forgo condoms.
If not, then use condoms. Or, consider PrEP for him, especially while you are trying to get pregnant. Some would say PrEP plus your being on effective HIV meds is like wearing a belt and suspenders at the same time, but if you are a look both ways before you cross, no walking under a ladder, insurance for your iPhone buying type, then this may be for you.