Blastocystis is

I can’t comment on combining Chinese herbs with the current western herbal formula you are using, but according to this study, the two herbs which showed the strongest effects on blastocystis in vitro were Ya Dan Zi and Huang Lian.

In general, however, you do not take Chinese herbal formulas this way - you first come to your diagnosis in Chinese Medicine terms and largely treat that (i.e. the underlying causes) and then tailor to your individual manifestations (see "how to choose a formula for more on that). I would suggest you consult directly with a Chinese Medicine herbalist in your area and have them create an appropriate formula for you.