12 weeks and 3 months are the same. In Uk, Canada and Australia guidlines, 12 weeks are conclusive. Even most of the experts follow the 12 weeks deadline.
Unprotected sex poses a risk of HIV transmission.
An HIV test at the right time gives you accurate results.
A 4th generation test should be done at 4 weeks post exposure and a simple HIV test at three months post exposure.
I would consider the result conclusive.
You could though confirm the negative result for the peace of your mind at three months.