does anyone know how much probiotics and/or echinacea I need to take when on antibiotics so I don't get thrush or yeast infection?

For adults it is recommended that they use 30,000 - 50,000 units of probiotics each day, & eat a clean diet (candida diet). The more strains of probiotics you can use the better you will be. I like using kefir as it has the most strains, but just be sure that you are using high potency probiotics that require refrigeration- they will be some of the most effective.

Most health food stores carry them.