I’m in no way a doctor or professional in this field; but I have read a lot about the different tests for HSV. You can find a plethora of excellent information on the Westover Heights Herpes page from Terri Warren who is an expert on the subject.
I can tell you that Ms. Warren and many other highly respected in the STI community consider the IgM HSV tests useless. It is a very flawed test with a common occurrence of false negatives. The IgG test is far more accurate, but you have to wait longer for a result. You can get a very accurate result 4-6 weeks post exposure, but it isn’t conclusive until you are tested 3 months post exposure. The Gold Standard is the Western Blot HSV test from the University of Washington. It is the most accurate test out there, but once again you need to wait 3 months+, and it’s only available through the UofW. There is also lots of info on Terri’s site about it as well, and you can go through her if you are wanting to take it.
Good luck, and stay calm. It’s definitely hard to do. I’m going through my own scare right now.