However, one crucial detail is missing. Syphilis never is confirmed by a single blood test -- there is a two test minimum. What test did you have other than the titered RPR? Probably it was done; knowledgeable doctors or clinics would not have treated you otherwise. (Well, one exception:  rather than a second blood test, if the ulcer(s) (chancres) were examined by dark field microscopy and syphilis bacteria identified, that usually is conclusive.)

Another red flag about syphilis is that you had a pretty low risk exposure. Although it certainly is possible your partner indeed had active syphilis transmissible by oral contact -- but the frequency of syphilis in female sex workers is low (in the US and Western Europe), and infectious lesions of the mouth are uncommon as well.

With those caveats, for now I'll assume the diagnosis was accurate. If so, you can be confident you were adequately treated, presumably with benzathine penicillin G (Bicillin®) -- as it seems you know already. The apparent healing of the ulcers is solid evidence of effective treatment. Accordingly, it is exceedingly unlikely your current rash is due to syphilis. In addition to the certainty of penicillin treatment, it's too soon for secondary syphilis to be the cause of your rash. Secondary syphilis generally occurs no sooner than 6 weeks and usually 2-3 months after primary syphilis. This course can be accelerated in HIV infected persons, but I assume you don't have HIV or you would have mentioned it.

I look forward to commenting further after learning about other tests and the certainty of the diagnosis. In the meantime, I hope these comments are helpful.

HHH, MD