H.pylori blood test igg positive and igm negative. i didn't treat h.pylori before the test. do i have h.pylori?

Hard to know: I believe that the prevalence of H. pylori is much higher in Phnom Penh than in most of the United States. Without knowing any specifics about the test that was used, I suspect the positive predictive value is high considering your location. This is increased given your history of gastritis. Treatment is straightforward and effective and should be considered.