I highly recommend testing from Dr. Amin's lab. Expert analysis for $164. Send in stool samples taken on days when your symptoms are the worst (important). I get symptoms on full moon so I took the sample the morning after and then 3 days after that. I was able to get the eggs in the sample and a positive ID. With an exact ID of your parasites, you can find out the treatment that will work on any specific worms you may have. It sounds like you are suffering from some type of parasite not treatable by pet meds, or some other GI illness.
Bless you and may you find the key to unlock the door to to a healthy life!