Pug that is eating poop?

i have a 1 1/2 yr old pug that eats its own poop we have tried every commercial product and taken her to the vet to make sure all is ok. the vet has no suggestions for us.any help? she does this all the time even in her crate at night we still have not been able to housebreak her because she just dosent hold it she just goes and will eat it.we tried putting dipers on her but she just tears them off and a mussel will not be a option because our vet said it would not be safe due to he being a pug with a very flat nose. HELP!