4 painless white bumps on my gumline. 2 are gone but another showed up. dentist told me they were herpes, but they've lasted over a month. what r they?

Herpes does not: Cause white bumps rather blisters that turn into ulcers and should not last for a month.

Dentist may be right: I would tend to agree with your dentist. These herpetic lesions can occur over and over again due to the way the virus infects the region. I would have the dentist further evaluate you and perhaps see if a prescription antiviral would be of help for you.