It's too bad proper testing wasn't done before treatment -- specifically, referral to an STD clinic for
a darkfield microscope test
, which is the may way to diagnose primary syphilis
at early stages. But depending on where you are, such testing might not have been easily available.
If you had syphilis, it would have been cured by the antibiotics you took; azithromycin usually is active against it, and doxycycline always is. Early cure often prevents the blood test from turning positive.