He cheated on me with his ex who has herpies

So I found out my husband has been cheating on me with his ex. And she has herpies... I made him get tested and he tested negative and he said that's because he never had sex with her since we have been married and We have been married for almost two years they have been talking on and off the whole time. If he has sex with her he would have mostlikly gotten herpies right?