Silent pelvic inflammatory disease (PID) is fallopian tube infection that doesn't cause the pain and fever that are hallmarks of classic PID. It certainly can occur, most commonly due to chlamydia, but there is no easy diagnosis for it. However, it sounds like your STD risk has been low, at least in the past 3 years.
So the chance you have had silent PID seems low--but I know nothing about your STD risk in distant past years. Most silent PID comes to light when a woman attempts to conceive and is unable to do so; the standard definition is a year of unprotected intercourse without conception. If that is your situation, see a gynecologist experienced in infertility diagnosis and management.
Good luck-- HHH, MD
I forgot to comment on your follow-up. No, neither the pap test itself nor a routine pelvic examination can tell if silent PID is present or has occurred previously. In other words, "silent" not only no symptoms, it means no overt abnormalities on routine testing. That's why it usually comes up in the context of an evaluation for infertility.
HHH, MD
I forgot to mention I go for a PAP every 6 months as I was diagnosed w/ a low grade of HPV. Could a doctor tell from a PAP if there was a suspicion of a PID?