Syphilis is uncommon in most developed countries, and since you used a condom, your risk is really low.
To get syphilis, your partner would have to have a syphilis sore to be contagious.
If you ever got syphilis, they have a treatment protocol for people who are allergic to penicillin, so you could still be treated successfully.
You can test for syphilis at 6 weeks.