You picked up a protozoa infection. You will need to do the Metametrix GI Effects Stool test (if you can't find anyone to do the test, pm me). Do not waste your $ doing outdating testing protocols.
Probiotics are useless (unless you have a bacterial situation going on) - protozoa eat bacteria so you are feeding them. Protozoa will not respond to grapefruit seed extract or any other herb :( Some of the lower protozoa like giardia may respond to the herb/supplments, but the heartier ones will not (personal experience).
Drug protocols are the only effective means of getting rid of them and the protocol depends upon the species of the protozoa. Go to badbugs.org and read some of the literature there, it will help you understand this better. Badbugs covers b. hominis, d. fragilis and e. histolytica however there are other protozoa that can infect you (besides giradia and cryptospordium).