Put a little (spoonful) crushed pineapple in the dog food. The enzymes in the pineapple do something to the poop that makes it smell unattractive even to the dog. It has always worked on my problem dogs.
The simple answer is physically there is probably nothing wrong with your dog but your dog may have mental issues or even suffer from an Obsessive Compulsive Disorder (OCD) to eat their own poop. The dog we had when we lived in Iceland used to eat his own poop too and it wasn't nothing a breath mint wouldn't almost fix. Just don't let the dog lick you or company on the face right afterward. Not only is butt to mouth unsanitary but according to US CODE 2257 it is illegal. LOL
For real, I doubt you have anything to worry about.