Chances that my HIV test were false negatives

Was having sex with this dude for most of September going into October. He let fly that he has slept with prostitutes in the past.

Almost two weeks after having sex with him I did an HIV Test, it was negative. Had sex with him a few more times. Then came November. I swerved him for the most part and then he left late November.

I did another HIV test in late December, a recommendation from my doctor. This one was a duo HIV/Syphillis test…both were negative.

How likely is that it was a false negative.