Diatomaceous Earth Food Grade

Anyone know where to buy the Food Grade Diatomaceous Earth? Ive tried Whole Foods and Sprouts which is what's near me.. I think Walmart sells a really big bag of it too. Im just wanting a small bag to try out. Also ive read online to take about 1 Tablespoonful a day.

Anyone know how long to do this to completely kill off parasites and worms? And has anyone used this product with success? Ive tried cleanses and done a colonic with some enemas hoping to get things moving along. Ive suffered from constipation my whole life, now have eczema, and a few other problems so I'm really wanting to try this out and see if itll clear up some things.

Dallas, TX area would be helpful if its a store or anywhere online thats reputable greatly appreciated!!!!!