There are blood tests for syphilolis avaiolable at no charge at the local department of health. They are conducted by nujmber and you don't have to giove your name.
I would also consider the possibiolity you have had a bits(s) by ticks infected with lyme disease. These bites are characterized by a "bulls-eye".
In any event, I would suggest you get peace-of-mind by having a professional opinion in-person by an M.D.