Your story sounds similar to mine. I became very sick after returning from Thailand - very sore upper stomach, extreme bloating and dizziness. Stool samples revealed Blastocystis Hominis (also considered a non pathogen). In the absense of any other problems I was treated with strong Anti-Biotics which seems to have killed the Blasto (I have had supsequent stool tests which were negative for Blasto).
I still, however am not well. I have stomach pain - way lees than b4, bloating - also way less than b4 and dizziness which has not subsided. In addtion I also now have a white tongue. My suspision is that the strong meds I have taken have disrupted the good bacteria in my gut and and given other bad species a chance to populate my gut.
In response I have now started on pro-biotics. I am taking VSL#3 twice a day at the moment. I also have an appointment with DR Tom Borody in Sydney next week (http://www.cdd.com.au) where we will talk about the possibility of human fecal infusion.