Very confused

i've been sick for about 2 years now, hypothyroid, low estrogen, possible candida, etc. anyway, i bought humaworm and have taken it for 2 days now, but i have a question- i'm confused about parasites being so bad for us. i thought we needed some parasites in our systems to take care of "bad" bacteria and such. it just seems odd that we would be trying to kill the things that naturally occur in our bodies and in nature. am i totally off-base here? thanks!