Mitchmurph is right.
Speaking as one who has had giardia TWICE ... you would know it if you had a parasitic infection. Bloody diarrhea 20 times a day is hard to miss. As are the carcinogenic drugs to kill the parasites (but you gotta take them).
If you really had parasites, getting rid of them would make you gain
weight, not lose it. Parasitic infections cause uncontrollable weight loss, like Mitch's friend.
If anyone thinks they have parasites, go to a doctor and get tested. The nasty little critters and their spores are microscopic, so you don't "see" them exit. They need to be cultured and looked at under a microscope. It's definitely not something to either self-diagnose or self-treat!