Islandmadre,
Welcome to the boards!!!
It depends on what kinds of symptoms you've had, what kinds of doctors you've seen, and other factors.
From personal experience I would say that when doctors test and test and test only to find "nothing", they have often overlooked the side effects of medication...so if you are taking medication of any kind, look for info about the side effects! Keep in mind that no one source lists ALL of the side effects so you will need to seek info from a variety of sources (pharmacists, drug companies, medication package inserts, etc). Also, keep in mind that those meds haven't been tested on everyone so some side effects may not be listed! I was in excellent health only to find myself with "arthritis", back pain, memory problems, mobility problems, restless legs, sleep disturbances,etc only to discover on my own (doctors were absolutely NO help here) that my problems and my rapid decline in health was due to the medication I was taking for high blood pressure.
I don't know what your situation is at all...but for your sake and the sake of others I will say it wouldn't hurt to review the Lyme Disease boards. Lyme Disease can affect multiple body systems...blood, heart, muscles, nerves, vision, bones,etc...and there is no one test that can detect the disease so doctors can't find anything wrong! As a result it often goes undetected and underreported, sometimes for decades.
Bethsheba