I believe that everybody has parasites, I also believe that in a healthy body and good immune system they dont cause too much problem. It's when the immune system runs down that the parasites leave the gut and set up in the organs. Just like Candida, it's not a problem until it migrates out of the digestive system.
I do understand, the cleansing making you ill. I started on the Bowel Cleanse and ran into a few problems myself but luckily I saw a therapist who told me not to cleanse at that time, as my body was not in a strong enough position to handle it. So I am building myself up first. Otherwise I may have become ill also. You always have to listen to your body, sometimes your mind interferes but always listen to your body.