You don't need to retest and actually didn't need to test the first time from your described exposure. Oral sex is not a risk for HIV even with an HIV+ partner. Air and saliva inactivate the virus. The only risks for HIV are to have unprotected vaginal or anal sex or to share IV drug needles. With that said, also, all 4th generation tests are conclusive at 28 days and beyond. So, no risk and no need to retest, you don't have hiv