There are several reasons why they could have become positive.
1) you're only undetectable at the time of the blood draw. The next day for whatever reason, your meds could just stop working and you become detectable again, but you would not know with just having a blood draw that says otherwise.
2) if you miss a few doses that's enough for the HIV to become detectable again until you get back on your meds.
3) or your partner could have been playing around with someone else who was detectable, whether they knew it or not.
4) if you're concerned about it, a HIV test can be done to see if it's the same DNA 🧬 virus that you have, to put your mind at ease or whether the HIV DNA 🧬 is different, then you'd know they were slutting around.
So there are several ways to become positive if your (or think you are) undetectable.
also like to add, your partner could have lied about their status, then after giving it to you, is trying to say you gave it to them.
Sounds suspicious.
How can HIV transmission occur even with an undetectable viral load?
This is an incredibly difficult situation, and it's understandable to feel confused and distressed. While having an undetectable viral load dramatically reduces transmission risk, it's important to verify that the viral load was truly undetectable at the Show Full Answer
@A myHIVteam Member
You do know it's a 2-edged sword. Careful, this partner might be trying to get something out of you claiming you infected them when they could have already been infected to start with. Your defenses seem to be in order if you are undetectable, you are more likely protected from this partner who may already be a carrier. Does this partner know about prep? It's too late anyway once infected, prep is no use. Good Luck!