In theory, IgM testing is positive soon after a new infection and later becomes negative, suggesting you have been infected
for at least several months, maybe
for years. However, the
IgM test is inherently unreliable.
Follow up with the dermatologist. Depending on what tests are available in your part of the country, you should have a type-specific blood test to distinguish HSV1 from HSV2; or in a future outbreak, the sores can be tested for the virus itself.