Since igm if the first antibody to appear after infection and may persist for weeks & if i know ive possibly recently been exposed to herpes in the past 3 weeks would my igm negative test be conclusive?

Herpes blood test: The HSV IgM test is useless. In theory it works like you say: early antibody is IgM and IgG comes later, so positive IgM and negative IgG should indicate early infection. But in herpes, IgG often appears earliest; IgM sometimes never develops; and positive IgM often is false. Rely on the IgG result only, but that take a few weeks. If no symptoms of herpes, it is likely you were not infected.