You did 8 tests. They were all negative. I don't think you need to do anymore.
Your negative test at 12 weeks was conclusive, which I told you before.
This is not a syphilis or testing issue. The tests are fine. You are not fine. You have an anxiety issue - a serious one. Doing 8 tests is not rational behavior. Doing 1, maybe 2 is - and it's pushing it since you had the conclusive test 12 weeks ago. Doing 8 is 6 years later is not.
You do not have syphilis. 9 tests have told you that.
I'm not judging you, I'm trying to help you. Really hear me on this - if I thought you had even a chance of syphilis, I'd tell you that. I don't. You need to talk to your doctor about anxiety and possible obsessive or compulsive thoughts/actions.
Mental health is as important as your physical health.
Also, how accurate would that be after so many years?