The only way to prove that your current outbreak is new is to have a culture test of the genital lesions turn out positive right now, and a blood test for the same type of herpes being negative right now. If a second blood test a few months later turns out positive it would confirm that this is a new infection since the blood upon new infection takes time to become positive. Please note that these blood tests are expensive and not readily available.
If it is Herpes type I, recurrences are less common than in type two, which also argues for new infection over re-activation. However, with herpes, as with any STD, a diagnosis shouldn't be about the blame game. What it should be about is good communication between you and your partner(s), education about the disease and the best way to stay healthy, and limiting transmission to others in the future.
To your health,
TALKING TO PARTNERS ADVICE
Keep our community healthy. Stop the spread by talking about STDs.