First, I am so sorry to have missed your post.
Without any index values for your IgG test, I can’t help you know how likely a false positive is. You could do a couple of things to get clarity:
First, an IgM should never have been done. Major labs have pulled this test and the CDC says never to use it due to high rates of false positive.
You could get testing done at a lab that gives index values, like Quest or LabCorp. They also give false positives, but at least you would know if you were in the low positive range (below 5) or not. In my experience and the reported data from Quest in one study, false positives in the low positive range can be about 50% of the time – this is very bad indeed.
Or you could go directly to the western blot, the gold standard test