I have this problem too...only it took me a yr and a half to figure out what it was! At first, I thought the tiny white things in my poop, were the sprinkles on the cookies I kept buying and eating. After stopping that, the perfectly round white things were still in my poop-I thought I had some strange, horrible problem! LOL Mostly, I thought maybe it was worm eggs!
I was too embarassed to ask my Dr. I finally told a friend about it, and it just happened that her aunt had had it for a while. She told me that it was probably medicine. I was only taking one med. in capsule form, so I opened it up, and Yep, It was the tiny balls in my capsules of Effexor (antidepressant). LOL