It would be helpful if you knew what you were dealing with. There are a number of pathogens that can harbor the gut, obviously parasites are one of those, but protozoa parasites can be there as well as bad bacteria and yeast/fungal strains. Optimally, it would be helpful to know what you are suffering with so you can tailor an attack, meaning there are certain treatments that work better than others.
ParaWellness Labs is a trusted lab for parasitic identification, Dr. Kevin Cahill is in NYC and is trusted as well.
Make sure you are using nutrients to support the body (b vitamins etc).