Plus, if the infection did last for 10 years (or more), might it be also possible you acquired it sometime before you met your long
At any rate, was your long
partner tested for Syphilis as well and treated if he was positive?
If not... I think it should be done in order to prevent the potential spread of the bacteria (though in latent stages and beyond, a person is no longer infectious - supposedly).
P.S. Relationships can be a bit tricky in terms of fidelity, etc.