You don't have herpes. Your latest (IgM) antibody test was falsely positive. Use the search link for 'herpes diagnosis' and 'IgM' to see many discussions on these points. The IgM HSV test is sometimes useful in diagnosing herpes in newborns, but it is useless in adults. Only IgG testing counts, and yours was negative. For sure you are not infected with HSV, either type 1 or type 2. (In some of the other discussions, you will find the names of researchers on IgM and other herpes blood tests--in case you want to refer your provider to the medical literature where he can learn accurate information about interpretation of the HSV blood tests.)
Your rash doesn't sound at all like herpes anyway. Herpes doews not cause the kinds of rash you decribe.
So taking the combination of your blood test results and the nature of the rash, you can forget herpes.
That covers questions 2 and 3. For question 1, all I can say with certainty is your rash isn't herpes. Tinea cruris (jock itch), folliculitis, and erythrasma all come to mind. But seeing a provider, preferably a dermatologist, is the way to know.
Good luck-- HHH, MD
Just to add due to space:
My treating doctor said the first one came back positive because the herpes anti-bodies had not fully developed. I found that weird, because if it was herpes, it would be 10 years old (i.e. plenty of time to develop). No way I could have gotten it more recently.
I think I have maybe had mouth blisters about 10 years ago.
You are absolutely right to consider it weird and not trust your doctor on this. He is wrong. See my reply above. Whatever your mouth blisters were, it wasn't oral herpes.
Why in the heck would a doctor do the first test?
Why not just skip to the second one?
Talk about adding unncessary worry and expense, geeshh!!!
The reasons the IgM test still is offered by some labs also have been discussed in the threads you can see by searching as I suggested above. Providers without particular knowledge about herpes typically order a "herpes blood test", without necessarily knowing exactly what tests the lab does. And labs not especially expert in herpes accept at face value what the test manufacturers tell them when the sell the test kits. Once a test is on the market, there is no regulatory control: later research may show the test doesn't work as originally thought, but there are no requirements that it come off the market. And the IgM HSV tests are dirt cheap to do, with a huge profit margin.
And there you are. Some major labs have stopped doing routine IgM HSV tests in adults, but many have not. Things probably will not change until enough patients like you complain with sufficient vigor that their docs in turn complain to the lab. (Hint, hint.)