Yes it is possible you have had HSV-2 for 16+ years without knowing it. But it is also possible your positive test is false. In order to interpret your test result, more information is necessary, i.e. the exact numerical valuues of your HerpeSelect tests for both HSV-1 and HSV-2. Here is a thread that explains why:
http://www.medhelp.org/posts/STDs/IGG-Test-Result-Confusion/show/593272
I did not say your symptoms are psychosomatic, only that they are not caused by any STD. They definitely are not caused by herpes, regardless of your test result. In other words, if your HSV-2 blood test is truly positive, then you have asymptomatic genital herpes plus another cause of your symptoms.
As to whether another "non STD organism" is responsible, I am doubtful. My guess is that you have the chronic pelvic pain syndrome, formerly considered a form of prostatitis -- but probably not due to infection and not likely to improve with ofloxacin or any other antibiotic. But still, if your doctor recommends antibiotic treatment, you should follow that advice and see if it helps. For more information about CPPS, google that term (spell it out), then start your reading with the excellent Wikipedia article and the information you can find from the Stanford University department of urology.