Not having chickenpox (and not being vaccinated for it) isn't really an advantage. Chickenpox as an adult is serious business: complications like pneumonia and encephalitis are much more common, and there's a significantly higher risk of death or hospitalization (75% of deaths from chickenpox are in adults, despite < 10% of the cases being in adults). You're also at higher risk for shingles if you catch it as an adult than as a child. Chickenpox is extremely contagious; it's airborne, can be transmitted just from being in the same area as someone with the disease for 15 minutes, and over 90% of people exposed will come down with the illness.

If you didn't get it as a kid you really should get vaccinated for it as an adult. Being exposed to the attenuated form of HHV-3 in the vaccine is way safer than actually catching the disease.

How do you know? Have you had HSV blood tests?