I would trust those test results. It's possible that your anxiety is causing a rash, or that it could be another STD, ....I don't know much about a home access test but maybe just have a doctor do another test. I'd say two negative test results are a good sign for sure.
Not a such thing as a 2nd generation DUO test. No you don't need to test at 6 months. Three months is conclusive.