What can cause white and/or black specks in stool - besides a particular food as this has been going on for months.

YOU ARE. STOOL "fixated" As long as you have NO SYMPTOMS and there is no BLOOD ...and you live in the USA (without foreign travel) the appearance is totally dietary related!
(BTW Your PCP can order a stool analysis for blood , parasites etc etc ..express your concerns ...you may "need " this to allow you to stop your "stool watching" compulsion!
Hope this helps