Welcome to the forum and thanks for your question, which is very intersting.
In fact, it seems quite likely you really do have HSV-2 of the central nervous system. You give a very typical story for a rare syndrome originally called Molleret's meningitis, for A French physician (pronounced Moleray) who first described recurrent aseptic (non-bacterial) meningitis of unknown cause. It was later called benign recurrent lymphocytic meningitis. As that name implies, it typically isn't serious ("benign"), but it tends to keep coming back ("recurrent"), and the main abnormal cells in the cerebrospinal fluid (CSF) are lymphocytes.
After decades of being recognized but the cause unknown, about 20 years ago -- with development of improved diagnostic tests -- it became apparent that most affected patients had positive blood tests for HSV-2; and that the virus could be found in CSF of the patients. About 10% of cases remain unexplained, but 90% of patients in fact have recurrent HSV-2 meningitis. HSV-2 also explains a fair proportion of people with non-recurrent (initial episode) non-bacterial meningitis. In addition, treatment with anti-HSV drugs like valacyclovir (which has no biolotical effect except to inhibit HSV) reduces the frequency and severity of recurrent episodes.
What's going on? Most such patients have unrecognized genital herpes, although some do have symptomatic genital herpes outbreaks from time to time. HSV-2 is tropic (attracted to) neural tissue; and in a small minority of cases, the virus migrates to and sets up infection in the central nervous system. When it reactivates, as HSV infections are prone to do, the result is recurrent meningitis.
The atypical feature in your case is your low positive HSV-2 IgG blood test. Most people have strongly positive results. However, the PCR test for HSV-2 in CSF usually is very reliable. I can't comment on the possibility that your PCR result is only weakly positive, but according to usual standards, you had a positive result -- i.e. HSV-2 DNA was present in your CSF during a typical episode of meningitis.
Your doctor is on the right track about further. However, I would recommend against the IgM test. IgM testing for HSV-2 is notoriously unreliable; here is a thread that discusses it:
http://www.medhelp.org/posts/show/248394 What you should have at this time is a Western blot test for HSV-2 antibody. WB is the gold standard for detection of HSV-2 antibody.
If your doctor is not an infectious diseases specialist, I strongly recommend you request consultation by one. He or she will be in the best position to assure the best diagnostic tests are done and, assuming HSV-2 infection is confirmed, to advise you about suppressive treatment and/or management of recurrent meningitis episodes.
In the meantime, don't be overly alarmed. As the name itself implies ("benign"), this is rarely serious. Of course there would be implications for future sexual partnerships, and you should be on the alert for possible mild symptoms of recurrent genital blisters or sores.
This may not be the reply you hoped to have, but I hope it is helpful to you. I'll be interested to hear the results of further diagnostic tests and the opinion of an ID consultant.
Best regards-- HHH, MD