I had three of the same symptoms as you back when I had Candida... chronic fatigue, chronic post nasal drip, and chronic bad breath. I also had IBS which from what you wrote it seems that you do too but not sure on that one.
Just from those three symptoms alone i'd say it's possible you have a Candida infection, but without a clinical diagnosis that's just me guessing which doesn't really do you too much good. Have you asked your doctor specifically about Candida?