For me it was a combination of having Blastocystis Hominis for many years, and my liver being toxic (due to Hep.A and Salmonella when I was a kid). I have been on a strict diet (no sugars, animal fat, wheat, etc.) with lots of fresh vegies and fruits; this combined with homeopathics and supplements, and my first flush about 3 weeks ago. I was starting to see a difference before the flush, but after, the healing sped up a whole lot quicker. The parasites did so much damage, that my body, after all those years just couldn't handle it anymore. I think that is why I got the nausea, and then when it progressed I had stomach aches, a heavy feeling in my stomach, I felt awful and exhausted every day.
I am so grateful that I was lead to the right holistic doctors (after regular meds couldn't help me). And now with the flush
I know I will be almost as good as new within a year (after being sick for 2).