Hello from JustAnswer.
It would be best if you can get seen as soon as possible. It is true that the general recommendation is to be seen within the first 3 days after a sexual encounter with an HIV positive individual, as post-exposure prophylaxis should be started within 3 days.
However, in those situations in which it is not known until after the three days that such an exposure occurred, it is still better to be checked as soon as possible, even if the only intervention
In your case, the fact that you have been taking Truvada starting on the night of the encounter actually means that you have been partially treated. Truvada alone is not a standard regimen for post-exposure prophylaxis, but it can be part of an appropriate regimen.
I would also note that a sexual encounter with an HIV positive individual with an undetectable viral load
has a much lower risk of HIV transmission. While it is clear that the risk is much lower, the actual numeric risk is not clear. The preliminary evidence is that the reduction in risk is greater than can be achieved with condom use. There are some ongoing studies to try to identify the actual numeric risk, but these results will likely not be known for a couple years. When you see your doctor, he/she may want verification that he had an undetectable viral load.
So, if he truly has an undetectable viral load, you risk would be much lower, but it still would be appropriate to be seen.
If I can provide any further information, please let me know.