I Have A Severe Giardia Infection (also "moderate Blastocystis Hominis).

I have a severe giardia infection (also "moderate blastocystis hominis). I am currently on a very high dose of Flagyl and am praying this takes care of it. This is my 3rd round of antibiotics. In the meantime, I can eat practically nothing. The mainstay of my diet is instant mashed potatoes, an occasional piece of dry toast, oddly enough plain yogurt. However, I find that I must eat VERY small amounts and very, very slowly not to be upset. I know the antibiotic could be part of the stomach upset. My question is: Assuming I don't go backward when the antibiotic is finished in a few days, how do I re-introduce food to my stomach? I've read nearly everything I can find on the web and know to avoid dairy (except it doesn't seem to bother me), citrus, caffeine, and alcohol. Thanks for any advice you can provide.