IGM is a worthless test to run for HSV. Doctors that run that test for HSV don't know how far off accurate that test is. First of all take some time to read
This goes into a lot of detail about IgM testing and sadly why it is off and useless for HSV. In your case it is impossible to tell when you were infected since you didn't have previous negative testing. Given the testing time frame chances are this is an old infection. Most adults have HSV-1 in the form of coldsores which we got as a kid from a kiss from our parents, grandparents, or that hot babe in school. The number you are seeing isn't a gague of how much antibody you have. it is just how sure the test is. That number will change even if you take the same blood sample and run it 10 times.
My suggestion is call off the S&D (Search and Determine) efforts. Chances are you have HSV-1 oral and not genital. Most people don't know they have HSV-1 because they can't remember having a cold sore. You are irritating yourself. I speak from experince...