I don't think Candida can cause parasites, it is a yeast overgrowth in your body.
I would imagine that most people get parasites from when they were kids, sticking things in their mouths, not washing their hands, drinking dirty hose water etc.
But there is a wide range of getting parasites as well, eating undercooked meat, including pork, fish etc. If you eat vegetables raw and don't wash them thoroughly etc. You can get them from the Library from a little kid who may have pin worms and stick your fingernail in your mouth, or get home and eat and forget to wash. Walk around just about anywhere bare foot.
It really isn't anything to be ashamed of :). It's quite normal, it's just coming around to the point that you are willing to do something about it. :)
They really are a part of our life. In most countries they deworm bi annually and like Humaworm says "We deworm our pets, why don't we deworm ourselves!"