She's not a high risk person as an ex girlfriend, correct? A one time exposure of unprotected sex is less than 2 percent chance of transmission so extremely low odds. However, as you know since you've go several posts here and have lots of answers, unprotected vaginal or anal sex with penetration are risks So, you a 4th generation test was appropriate. If you took it 28 days or more past the event and it was negative, it is conclusive. You do not have HIV.